1 /* Copyright (C) 2007 The PARI group.
2
3 This file is part of the PARI/GP package.
4
5 PARI/GP is free software; you can redistribute it and/or modify it under the
6 terms of the GNU General Public License as published by the Free Software
7 Foundation; either version 2 of the License, or (at your option) any later
8 version. It is distributed in the hope that it will be useful, but WITHOUT
9 ANY WARRANTY WHATSOEVER.
10
11 Check the License for details. You should have received a copy of it, along
12 with the package; see the file 'COPYING'. If not, write to the Free Software
13 Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA. */
14
15 #include "pari.h"
16 #include "paripriv.h"
17
18 /* Not so fast arithmetic with polynomials over F_2 */
19
20 /***********************************************************************/
21 /** **/
22 /** F2x **/
23 /** **/
24 /***********************************************************************/
25 /* F2x objects are defined as follows:
26 An F2x is a t_VECSMALL:
27 x[0] = codeword
28 x[1] = evalvarn(variable number) (signe is not stored).
29 x[2] = a_0...a_31 x[3] = a_32..a_63, etc. on 32bit
30 x[2] = a_0...a_63 x[3] = a_64..a_127, etc. on 64bit
31
32 where the a_i are bits.
33
34 signe(x) is not valid. Use lgpol(x)!=0 instead.
35 Note: pol0_F2x=pol0_Flx and pol1_F2x=pol1_Flx
36 */
37
38 INLINE long
F2x_degreespec(GEN x,long l)39 F2x_degreespec(GEN x, long l)
40 {
41 return (l==0)?-1:l*BITS_IN_LONG-bfffo(x[l-1])-1;
42 }
43
44 INLINE long
F2x_degree_lg(GEN x,long l)45 F2x_degree_lg(GEN x, long l)
46 {
47 return (l==2)?-1:bit_accuracy(l)-bfffo(x[l-1])-1;
48 }
49
50 long
F2x_degree(GEN x)51 F2x_degree(GEN x)
52 {
53 return F2x_degree_lg(x, lg(x));
54 }
55
56 GEN
monomial_F2x(long d,long vs)57 monomial_F2x(long d, long vs)
58 {
59 long l=nbits2lg(d+1);
60 GEN z = zero_zv(l-1);
61 z[1] = vs;
62 F2x_set(z,d);
63 return z;
64 }
65
66 GEN
F2x_to_ZX(GEN x)67 F2x_to_ZX(GEN x)
68 {
69 long l = 3+F2x_degree(x), lx = lg(x);
70 GEN z = cgetg(l,t_POL);
71 long i, j ,k;
72 for (i=2, k=2; i<lx; i++)
73 for (j=0; j<BITS_IN_LONG && k<l; j++,k++)
74 gel(z,k) = (x[i]&(1UL<<j))?gen_1:gen_0;
75 z[1]=evalsigne(l>=3)|x[1];
76 return z;
77 }
78
79 GEN
F2x_to_Flx(GEN x)80 F2x_to_Flx(GEN x)
81 {
82 long l = 3+F2x_degree(x), lx = lg(x);
83 GEN z = cgetg(l,t_VECSMALL);
84 long i, j, k;
85 z[1] = x[1];
86 for (i=2, k=2; i<lx; i++)
87 for (j=0; j<BITS_IN_LONG && k<l; j++,k++)
88 z[k] = (x[i]>>j)&1UL;
89 return z;
90 }
91
92 GEN
F2x_to_F2xX(GEN z,long sv)93 F2x_to_F2xX(GEN z, long sv)
94 {
95 long i, d = F2x_degree(z);
96 GEN x = cgetg(d+3,t_POL);
97 for (i=0; i<=d; i++)
98 gel(x,i+2) = F2x_coeff(z,i) ? pol1_F2x(sv): pol0_F2x(sv);
99 x[1] = evalsigne(d+1!=0)| z[1]; return x;
100 }
101
102 GEN
Z_to_F2x(GEN x,long sv)103 Z_to_F2x(GEN x, long sv)
104 {
105 return mpodd(x) ? pol1_F2x(sv): pol0_F2x(sv);
106 }
107
108 GEN
ZX_to_F2x(GEN x)109 ZX_to_F2x(GEN x)
110 {
111 long lx = lg(x), l = nbits2lg(lx-2);
112 GEN z = cgetg(l,t_VECSMALL);
113 long i, j, k;
114 z[1] = ((ulong)x[1])&VARNBITS;
115 for (i=2, k=1,j=BITS_IN_LONG; i<lx; i++,j++)
116 {
117 if (j==BITS_IN_LONG)
118 {
119 j=0; z[++k]=0;
120 }
121 if (mpodd(gel(x,i)))
122 z[k] |= 1UL<<j;
123 }
124 return F2x_renormalize(z,l);
125 }
126
127 GEN
Flx_to_F2x(GEN x)128 Flx_to_F2x(GEN x)
129 {
130 long lx = lg(x), l = nbits2lg(lx-2);
131 GEN z = cgetg(l,t_VECSMALL);
132 long i, j, k;
133 z[1] = x[1];
134 for (i=2, k=1, j=BITS_IN_LONG; i<lx; i++,j++)
135 {
136 if (j==BITS_IN_LONG)
137 {
138 j=0; z[++k] = 0;
139 }
140 if (x[i]&1UL)
141 z[k] |= 1UL<<j;
142 }
143 return F2x_renormalize(z,l);
144 }
145
146 GEN
F2x_to_F2v(GEN x,long N)147 F2x_to_F2v(GEN x, long N)
148 {
149 long i, l = lg(x);
150 long n = nbits2lg(N);
151 GEN z = cgetg(n,t_VECSMALL);
152 z[1] = N;
153 for (i=2; i<l ; i++) z[i]=x[i];
154 for ( ; i<n; i++) z[i]=0;
155 return z;
156 }
157
158 GEN
RgX_to_F2x(GEN x)159 RgX_to_F2x(GEN x)
160 {
161 long l=nbits2lg(lgpol(x));
162 GEN z=cgetg(l,t_VECSMALL);
163 long i,j,k;
164 z[1]=((ulong)x[1])&VARNBITS;
165 for(i=2, k=1,j=BITS_IN_LONG;i<lg(x);i++,j++)
166 {
167 if (j==BITS_IN_LONG)
168 {
169 j=0; k++; z[k]=0;
170 }
171 if (Rg_to_F2(gel(x,i)))
172 z[k]|=1UL<<j;
173 }
174 return F2x_renormalize(z,l);
175 }
176
177 /* If x is a POLMOD, assume modulus is a multiple of T. */
178 GEN
Rg_to_F2xq(GEN x,GEN T)179 Rg_to_F2xq(GEN x, GEN T)
180 {
181 long ta, tx = typ(x), v = get_F2x_var(T);
182 GEN a, b;
183 if (is_const_t(tx))
184 {
185 if (tx == t_FFELT) return FF_to_F2xq(x);
186 return Rg_to_F2(x)? pol1_F2x(v): pol0_F2x(v);
187 }
188 switch(tx)
189 {
190 case t_POLMOD:
191 b = gel(x,1);
192 a = gel(x,2); ta = typ(a);
193 if (is_const_t(ta)) return Rg_to_F2(a)? pol1_F2x(v): pol0_F2x(v);
194 b = RgX_to_F2x(b); if (b[1] != v) break;
195 a = RgX_to_F2x(a); if (F2x_equal(b,T)) return a;
196 if (lgpol(F2x_rem(b,T))==0) return F2x_rem(a, T);
197 break;
198 case t_POL:
199 x = RgX_to_F2x(x);
200 if (x[1] != v) break;
201 return F2x_rem(x, T);
202 case t_RFRAC:
203 a = Rg_to_F2xq(gel(x,1), T);
204 b = Rg_to_F2xq(gel(x,2), T);
205 return F2xq_div(a,b, T);
206 }
207 pari_err_TYPE("Rg_to_F2xq",x);
208 return NULL; /* LCOV_EXCL_LINE */
209 }
210
211 ulong
F2x_eval(GEN P,ulong x)212 F2x_eval(GEN P, ulong x)
213 {
214 if (odd(x))
215 {
216 long i, lP = lg(P);
217 ulong c = 0;
218 for (i=2; i<lP; i++)
219 c ^= P[i];
220 #ifdef LONG_IS_64BIT
221 c ^= c >> 32;
222 #endif
223 c ^= c >> 16;
224 c ^= c >> 8;
225 c ^= c >> 4;
226 c ^= c >> 2;
227 c ^= c >> 1;
228 return c & 1;
229 }
230 else return F2x_coeff(P,0);
231 }
232
233 GEN
F2x_add(GEN x,GEN y)234 F2x_add(GEN x, GEN y)
235 {
236 long i,lz;
237 GEN z;
238 long lx=lg(x);
239 long ly=lg(y);
240 if (ly>lx) swapspec(x,y, lx,ly);
241 lz = lx; z = cgetg(lz, t_VECSMALL); z[1]=x[1];
242 for (i=2; i<ly; i++) z[i] = x[i]^y[i];
243 for ( ; i<lx; i++) z[i] = x[i];
244 return F2x_renormalize(z, lz);
245 }
246
247 static GEN
F2x_addspec(GEN x,GEN y,long lx,long ly)248 F2x_addspec(GEN x, GEN y, long lx, long ly)
249 {
250 long i,lz;
251 GEN z;
252
253 if (ly>lx) swapspec(x,y, lx,ly);
254 lz = lx+2; z = cgetg(lz, t_VECSMALL) + 2;
255 for (i=0; i<ly-3; i+=4)
256 {
257 z[i] = x[i]^y[i];
258 z[i+1] = x[i+1]^y[i+1];
259 z[i+2] = x[i+2]^y[i+2];
260 z[i+3] = x[i+3]^y[i+3];
261 }
262 for (; i<ly; i++)
263 z[i] = x[i]^y[i];
264 for ( ; i<lx; i++) z[i] = x[i];
265 z -= 2; z[1] = 0; return F2x_renormalize(z, lz);
266 }
267
268 GEN
F2x_1_add(GEN y)269 F2x_1_add(GEN y)
270 {
271 GEN z;
272 long lz, i;
273 if (!lgpol(y))
274 return pol1_F2x(y[1]);
275 lz=lg(y);
276 z=cgetg(lz,t_VECSMALL);
277 z[1] = y[1];
278 z[2] = y[2]^1UL;
279 for(i=3;i<lz;i++)
280 z[i] = y[i];
281 if (lz==3) z = F2x_renormalize(z,lz);
282 return z;
283 }
284
285 INLINE void
F2x_addshiftipspec(GEN x,GEN y,long ny,ulong db)286 F2x_addshiftipspec(GEN x, GEN y, long ny, ulong db)
287 {
288 long i;
289 if (db)
290 {
291 ulong dc=BITS_IN_LONG-db;
292 ulong r=0, yi;
293 for(i=0; i<ny-3; i+=4)
294 {
295 yi = uel(y,i); x[i] ^= (yi<<db)|r; r = yi>>dc;
296 yi = uel(y,i+1); x[i+1] ^= (yi<<db)|r; r = yi>>dc;
297 yi = uel(y,i+2); x[i+2] ^= (yi<<db)|r; r = yi>>dc;
298 yi = uel(y,i+3); x[i+3] ^= (yi<<db)|r; r = yi>>dc;
299 }
300 for( ; i<ny; i++)
301 {
302 ulong yi = uel(y,i); x[i] ^= (yi<<db)|r; r = yi>>dc;
303 }
304 if (r) x[i] ^= r;
305 }
306 else
307 {
308 for(i=0; i<ny-3; i+=4)
309 {
310 x[i] ^= y[i];
311 x[i+1] ^= y[i+1];
312 x[i+2] ^= y[i+2];
313 x[i+3] ^= y[i+3];
314 }
315 for( ; i<ny; i++)
316 x[i] ^= y[i];
317 }
318 }
319
320 INLINE void
F2x_addshiftip(GEN x,GEN y,ulong d)321 F2x_addshiftip(GEN x, GEN y, ulong d)
322 {
323 ulong db, dl=dvmduBIL(d, &db);
324 F2x_addshiftipspec(x+2+dl, y+2, lgpol(y), db);
325 }
326
327 static GEN
F2x_mul1(ulong x,ulong y)328 F2x_mul1(ulong x, ulong y)
329 {
330 ulong x1=(x&HIGHMASK)>>BITS_IN_HALFULONG;
331 ulong x2=x&LOWMASK;
332 ulong y1=(y&HIGHMASK)>>BITS_IN_HALFULONG;
333 ulong y2=y&LOWMASK;
334 ulong r1,r2,rr;
335 GEN z;
336 ulong i;
337 rr=r1=r2=0UL;
338 if (x2)
339 for(i=0;i<BITS_IN_HALFULONG;i++)
340 if (x2&(1UL<<i))
341 {
342 r2^=y2<<i;
343 rr^=y1<<i;
344 }
345 if (x1)
346 for(i=0;i<BITS_IN_HALFULONG;i++)
347 if (x1&(1UL<<i))
348 {
349 r1^=y1<<i;
350 rr^=y2<<i;
351 }
352 r2^=(rr&LOWMASK)<<BITS_IN_HALFULONG;
353 r1^=(rr&HIGHMASK)>>BITS_IN_HALFULONG;
354 z=cgetg((r1?4:3),t_VECSMALL);
355 z[2]=r2;
356 if (r1) z[3]=r1;
357 return z;
358 }
359
360 static GEN
F2x_mulspec_basecase(GEN x,GEN y,long nx,long ny)361 F2x_mulspec_basecase(GEN x, GEN y, long nx, long ny)
362 {
363 long l, i, j;
364 GEN z;
365 l = nx + ny;
366 z = zero_Flv(l+1);
367 for(i=0; i < ny-1; i++)
368 {
369 GEN zi = z+2+i;
370 ulong yi = uel(y,i);
371 if (yi)
372 for(j=0; j < BITS_IN_LONG; j++)
373 if (yi&(1UL<<j)) F2x_addshiftipspec(zi,x,nx,j);
374 }
375 {
376 GEN zi = z+2+i;
377 ulong yi = uel(y,i);
378 long c = BITS_IN_LONG-bfffo(yi);
379 for(j=0; j < c; j++)
380 if (yi&(1UL<<j)) F2x_addshiftipspec(zi,x,nx,j);
381 }
382 return F2x_renormalize(z, l+2);
383 }
384
385 static GEN
F2x_addshift(GEN x,GEN y,long d)386 F2x_addshift(GEN x, GEN y, long d)
387 {
388 GEN xd,yd,zd = (GEN)avma;
389 long a,lz,ny = lgpol(y), nx = lgpol(x);
390 long vs = x[1];
391 if (nx == 0) return y;
392 x += 2; y += 2; a = ny-d;
393 if (a <= 0)
394 {
395 lz = (a>nx)? ny+2: nx+d+2;
396 (void)new_chunk(lz); xd = x+nx; yd = y+ny;
397 while (xd > x) *--zd = *--xd;
398 x = zd + a;
399 while (zd > x) *--zd = 0;
400 }
401 else
402 {
403 xd = new_chunk(d); yd = y+d;
404 x = F2x_addspec(x,yd,nx,a);
405 lz = (a>nx)? ny+2: lg(x)+d;
406 x += 2; while (xd > x) *--zd = *--xd;
407 }
408 while (yd > y) *--zd = *--yd;
409 *--zd = vs;
410 *--zd = evaltyp(t_VECSMALL) | evallg(lz); return zd;
411 }
412
413 /* shift polynomial + gerepile */
414 /* Do not set evalvarn. Cf Flx_shiftip */
415 static GEN
F2x_shiftip(pari_sp av,GEN x,long v)416 F2x_shiftip(pari_sp av, GEN x, long v)
417 {
418 long i, lx = lg(x), ly;
419 GEN y;
420 if (!v || lx==2) return gerepileuptoleaf(av, x);
421 ly = lx + v;
422 (void)new_chunk(ly); /* check that result fits */
423 x += lx; y = (GEN)av;
424 for (i = 2; i<lx; i++) *--y = *--x;
425 for (i = 0; i< v; i++) *--y = 0;
426 y -= 2; y[0] = evaltyp(t_VECSMALL) | evallg(ly);
427 return gc_const((pari_sp)y, y);
428 }
429
430 static GEN
F2x_to_int(GEN a,long na,long da,long bs)431 F2x_to_int(GEN a, long na, long da, long bs)
432 {
433 const long BIL = BITS_IN_LONG;
434 GEN z, zs;
435 long i,j,k,m;
436 long lz = nbits2lg(1+da*bs);
437 z = cgeti(lz); z[1] = evalsigne(1)|evallgefint(lz);
438 zs = int_LSW(z); *zs = 0;
439 for (i=0, k=2, m=0; i<na; i++)
440 for (j=0; j<BIL; j++, m+=bs)
441 {
442 if (m >= BIL)
443 {
444 k++; if (k>=lz) break;
445 zs = int_nextW(zs);
446 *zs = 0;
447 m -= BIL;
448 }
449 *zs |= ((a[i]>>j)&1UL)<<m;
450 }
451 return int_normalize(z,0);
452 }
453
454 static GEN
int_to_F2x(GEN x,long d,long bs)455 int_to_F2x(GEN x, long d, long bs)
456 {
457 const long BIL = BITS_IN_LONG;
458 long lx = lgefint(x), lz = nbits2lg(d+1);
459 long i,j,k,m;
460 GEN xs = int_LSW(x);
461 GEN z = cgetg(lz, t_VECSMALL);
462 z[1] = 0;
463 for (k=2, i=2, m=0; k < lx; i++)
464 {
465 z[i] = 0;
466 for (j=0; j<BIL; j++, m+=bs)
467 {
468 if (m >= BIL)
469 {
470 if (++k==lx) break;
471 xs = int_nextW(xs);
472 m -= BIL;
473 }
474 if ((*xs>>m)&1UL)
475 z[i]|=1UL<<j;
476 }
477 }
478 return F2x_renormalize(z,lz);
479 }
480
481 static GEN
F2x_mulspec_mulii(GEN a,GEN b,long na,long nb)482 F2x_mulspec_mulii(GEN a, GEN b, long na, long nb)
483 {
484 long da = F2x_degreespec(a,na), db = F2x_degreespec(b,nb);
485 long bs = expu(1 + maxss(da, db))+1;
486 GEN A = F2x_to_int(a,na,da,bs);
487 GEN B = F2x_to_int(b,nb,db,bs);
488 GEN z = mulii(A,B);
489 return int_to_F2x(z,da+db,bs);
490 }
491
492 /* fast product (Karatsuba) of polynomials a,b. These are not real GENs, a+2,
493 * b+2 were sent instead. na, nb = number of terms of a, b.
494 * Only c, c0, c1, c2 are genuine GEN.
495 */
496 static GEN
F2x_mulspec(GEN a,GEN b,long na,long nb)497 F2x_mulspec(GEN a, GEN b, long na, long nb)
498 {
499 GEN a0,c,c0;
500 long n0, n0a, i, v = 0;
501 pari_sp av;
502 while (na && !a[0]) { a++; na-=1; v++; }
503 while (nb && !b[0]) { b++; nb-=1; v++; }
504 if (na < nb) swapspec(a,b, na,nb);
505 if (!nb) return pol0_F2x(0);
506
507 av = avma;
508 if (na == 1)
509 return F2x_shiftip(av, F2x_mul1(*a,*b), v);
510 if (na < F2x_MUL_KARATSUBA_LIMIT)
511 return F2x_shiftip(av, F2x_mulspec_basecase(a, b, na, nb), v);
512 if (nb >= F2x_MUL_MULII_LIMIT)
513 return F2x_shiftip(av, F2x_mulspec_mulii(a, b, na, nb), v);
514 i=(na>>1); n0=na-i; na=i;
515 a0=a+n0; n0a=n0;
516 while (n0a && !a[n0a-1]) n0a--;
517
518 if (nb > n0)
519 {
520 GEN b0,c1,c2;
521 long n0b;
522
523 nb -= n0; b0 = b+n0; n0b = n0;
524 while (n0b && !b[n0b-1]) n0b--;
525 c = F2x_mulspec(a,b,n0a,n0b);
526 c0 = F2x_mulspec(a0,b0,na,nb);
527
528 c2 = F2x_addspec(a0,a,na,n0a);
529 c1 = F2x_addspec(b0,b,nb,n0b);
530
531 c1 = F2x_mul(c1,c2);
532 c2 = F2x_add(c0,c);
533
534 c2 = F2x_add(c1,c2);
535 c0 = F2x_addshift(c0,c2,n0);
536 }
537 else
538 {
539 c = F2x_mulspec(a,b,n0a,nb);
540 c0 = F2x_mulspec(a0,b,na,nb);
541 }
542 c0 = F2x_addshift(c0,c,n0);
543 return F2x_shiftip(av,c0, v);
544 }
545
546 GEN
F2x_mul(GEN x,GEN y)547 F2x_mul(GEN x, GEN y)
548 {
549 GEN z = F2x_mulspec(x+2,y+2, lgpol(x),lgpol(y));
550 z[1] = x[1]; return z;
551 }
552
553 GEN
F2x_sqr(GEN x)554 F2x_sqr(GEN x)
555 {
556 const ulong sq[]={0,1,4,5,16,17,20,21,64,65,68,69,80,81,84,85};
557 long i,ii,j,jj;
558 long lx=lg(x), lz=2+((lx-2)<<1);
559 GEN z;
560 z = cgetg(lz, t_VECSMALL); z[1]=x[1];
561 for (j=2,jj=2;j<lx;j++,jj++)
562 {
563 ulong x1=((ulong)x[j]&HIGHMASK)>>BITS_IN_HALFULONG;
564 ulong x2=(ulong)x[j]&LOWMASK;
565 z[jj]=0;
566 if (x2)
567 for(i=0,ii=0;i<BITS_IN_HALFULONG;i+=4,ii+=8)
568 z[jj]|=sq[(x2>>i)&15UL]<<ii;
569 z[++jj]=0;
570 if (x1)
571 for(i=0,ii=0;i<BITS_IN_HALFULONG;i+=4,ii+=8)
572 z[jj]|=sq[(x1>>i)&15UL]<<ii;
573 }
574 return F2x_renormalize(z, lz);
575 }
576
577 static GEN
F2x_pow2n(GEN x,long n)578 F2x_pow2n(GEN x, long n)
579 {
580 long i;
581 for(i=1;i<=n;i++)
582 x = F2x_sqr(x);
583 return x;
584 }
585
586 int
F2x_issquare(GEN x)587 F2x_issquare(GEN x)
588 {
589 const ulong mask = (ULONG_MAX/3UL)*2;
590 ulong i, lx = lg(x);
591 for (i=2; i<lx; i++)
592 if ((x[i]&mask)) return 0;
593 return 1;
594 }
595
596 /* Assume x is a perfect square */
597 GEN
F2x_sqrt(GEN x)598 F2x_sqrt(GEN x)
599 {
600 const ulong sq[]={0,1,4,5,2,3,6,7,8,9,12,13,10,11,14,15};
601 long i,ii,j,jj;
602 long lx=lg(x), lz=2+((lx-1)>>1);
603 GEN z;
604 z = cgetg(lz, t_VECSMALL); z[1]=x[1];
605 for (j=2,jj=2;jj<lz;j++,jj++)
606 {
607 ulong x2=x[j++];
608 z[jj]=0;
609 if (x2)
610 for(i=0,ii=0;ii<BITS_IN_HALFULONG;i+=8,ii+=4)
611 {
612 ulong rl = (x2>>i)&15UL, rh = (x2>>(i+4))&15UL;
613 z[jj]|=sq[rl|(rh<<1)]<<ii;
614 }
615 if (j<lx)
616 {
617 x2 = x[j];
618 if (x2)
619 for(i=0,ii=0;ii<BITS_IN_HALFULONG;i+=8,ii+=4)
620 {
621 ulong rl = (x2>>i)&15UL, rh = (x2>>(i+4))&15UL;
622 z[jj]|=(sq[rl|(rh<<1)]<<ii)<<BITS_IN_HALFULONG;
623 }
624 }
625 }
626 return F2x_renormalize(z, lz);
627 }
628
629 static GEN
F2x_shiftneg(GEN y,ulong d)630 F2x_shiftneg(GEN y, ulong d)
631 {
632 long db, dl=dvmdsBIL(d, &db);
633 long i, ly = lg(y), lx = ly-dl;
634 GEN x = cgetg(lx, t_VECSMALL);
635 x[1] = y[1];
636 if (db)
637 {
638 ulong dc=BITS_IN_LONG-db;
639 ulong r=0;
640 for(i=lx-1; i>=2; i--)
641 {
642 x[i] = (((ulong)y[i+dl])>>db)|r;
643 r = ((ulong)y[i+dl])<<dc;
644 }
645 }
646 else
647 for(i=2; i<lx; i++)
648 x[i] = y[i+dl];
649 return F2x_renormalize(x,lx);
650 }
651
652 static GEN
F2x_shiftpos(GEN y,ulong d)653 F2x_shiftpos(GEN y, ulong d)
654 {
655 long db, dl=dvmdsBIL(d, &db);
656 long i, ly = lg(y), lx = ly+dl+(!!db);
657 GEN x = cgetg(lx, t_VECSMALL);
658 x[1] = y[1]; for(i=0; i<dl; i++) x[i+2] = 0;
659 if (db)
660 {
661 ulong dc=BITS_IN_LONG-db;
662 ulong r=0;
663 for(i=2; i<ly; i++)
664 {
665 x[i+dl] = (((ulong)y[i])<<db)|r;
666 r = ((ulong)y[i])>>dc;
667 }
668 x[i+dl] = r;
669 }
670 else
671 for(i=2; i<ly; i++)
672 x[i+dl] = y[i];
673 return F2x_renormalize(x,lx);
674 }
675
676 GEN
F2x_shift(GEN y,long d)677 F2x_shift(GEN y, long d)
678 {
679 return d<0 ? F2x_shiftneg(y,-d): F2x_shiftpos(y,d);
680 }
681
682 #define F2x_recip2(pk,m) u = ((u&m)<<pk)|((u&(~m))>>pk);
683 #define F2x_recipu(pk) F2x_recip2(pk,((~0UL)/((1UL<<pk)+1)))
684
685 static ulong
F2x_recip1(ulong u)686 F2x_recip1(ulong u)
687 {
688 u = (u<<BITS_IN_HALFULONG)|(u>>BITS_IN_HALFULONG);
689 #ifdef LONG_IS_64BIT
690 F2x_recipu(16);
691 #endif
692 F2x_recipu(8);
693 F2x_recipu(4);
694 F2x_recipu(2);
695 F2x_recipu(1);
696 return u;
697 }
698
699 static GEN
F2x_recip_raw(GEN x)700 F2x_recip_raw(GEN x)
701 {
702 long i, l;
703 GEN y = cgetg_copy(x,&l);
704 y[1] = x[1];
705 for (i=0; i<l-2; i++)
706 uel(y,l-1-i) = F2x_recip1(uel(x,2+i));
707 return y;
708 }
709
710 GEN
F2x_recip(GEN x)711 F2x_recip(GEN x)
712 {
713 long lb = remsBIL(F2x_degree(x)+1);
714 GEN y = F2x_recip_raw(x);
715 if (lb) y = F2x_shiftneg(y,BITS_IN_LONG-lb);
716 return y;
717 }
718
719 GEN
F2xn_red(GEN f,long n)720 F2xn_red(GEN f, long n)
721 {
722 GEN g;
723 long i, dl, db, l;
724 if (F2x_degree(f) < n) return zv_copy(f);
725 dl = dvmdsBIL(n, &db); l = 2 + dl + (db>0);
726 g = cgetg(l, t_VECSMALL);
727 g[1] = f[1];
728 for (i=2; i<l; i++)
729 uel(g,i) = uel(f,i);
730 if (db) uel(g,l-1) = uel(f,l-1)&((1UL<<db)-1);
731 return F2x_renormalize(g, l);
732 }
733
734 static GEN
F2xn_mul(GEN a,GEN b,long n)735 F2xn_mul(GEN a, GEN b, long n) { return F2xn_red(F2x_mul(a, b), n); }
736
737 static ulong
F2xn_inv_basecase1(ulong x)738 F2xn_inv_basecase1(ulong x)
739 {
740 ulong u, v, w;
741 long i;
742 u = x>>1;
743 v = (u&1UL)|2UL;
744 w = u&v; w ^= w >> 1; v = (w&1UL)|(v<<1);
745 w = u&v; w ^= w >> 2; w ^= w >> 1; v = (w&1UL)|(v<<1);
746 w = u&v; w ^= w >> 2; w ^= w >> 1; v = (w&1UL)|(v<<1);
747 for (i=1;i<=4;i++)
748 { w = u&v; w ^= w >> 4; w ^= w >> 2; w ^= w >> 1; v = (w&1UL)|(v<<1); }
749 for (i=1;i<=8;i++)
750 { w = u&v; w ^= w >> 8; w ^= w >> 4; w ^= w >> 2; w ^= w >> 1; v = (w&1UL)|(v<<1); }
751 for (i=1;i<=16;i++)
752 { w = u&v; w ^= w >> 16; w ^= w >> 8; w ^= w >> 4; w ^= w >> 2; w ^= w >> 1; v = (w&1UL)|(v<<1); }
753 #ifdef LONG_IS_64BIT
754 for (i=1; i<=32; i++)
755 { w = u&v; w ^= w >> 32; w ^= w >> 16; w ^= w >> 8; w ^= w >> 4; w ^= w >> 2; w ^= w >> 1;
756 v = (w&1UL)|(v<<1); }
757 #endif
758 return (F2x_recip1(v)<<1)|1UL;
759 }
760
761 static GEN
F2xn_inv1(GEN v,long e)762 F2xn_inv1(GEN v, long e)
763 {
764 ulong mask = e==BITS_IN_LONG ? -1UL: ((1UL<<e)-1);
765 return mkvecsmall2(v[1],F2xn_inv_basecase1(uel(v,2))&mask);
766 }
767
768 GEN
F2xn_inv(GEN f,long e)769 F2xn_inv(GEN f, long e)
770 {
771 pari_sp av = avma, av2;
772 ulong mask;
773 GEN W;
774 long n=1;
775 if (lg(f)==2) pari_err_INV("Flxn_inv",f);
776 if (e <= BITS_IN_LONG) return F2xn_inv1(f, e);
777 W = F2xn_inv1(f, BITS_IN_LONG);
778 mask = quadratic_prec_mask(divsBIL(e+BITS_IN_LONG-1));
779 n = BITS_IN_LONG;
780 av2 = avma;
781 for (;mask>1;)
782 {
783 GEN u, fr;
784 long n2 = n;
785 n<<=1; if (mask & 1) n--;
786 mask >>= 1;
787 fr = F2xn_red(f, n);
788 u = F2x_shift(F2xn_mul(W, fr, n), -n2);
789 W = F2x_add(W, F2x_shift(F2xn_mul(u, W, n-n2), n2));
790 if (gc_needed(av2,2))
791 {
792 if(DEBUGMEM>1) pari_warn(warnmem,"F2xn_inv, e = %ld", n);
793 W = gerepileupto(av2, W);
794 }
795 }
796 return gerepileupto(av, F2xn_red(W,e));
797 }
798
799 GEN
F2x_get_red(GEN T)800 F2x_get_red(GEN T)
801 {
802 return T;
803 }
804
805 /* separate from F2x_divrem for maximal speed. */
806 GEN
F2x_rem(GEN x,GEN y)807 F2x_rem(GEN x, GEN y)
808 {
809 long dx,dy;
810 long lx=lg(x);
811 dy = F2x_degree(y); if (!dy) return pol0_F2x(x[1]);
812 dx = F2x_degree_lg(x,lx);
813 x = F2x_copy(x);
814 while (dx>=dy)
815 {
816 F2x_addshiftip(x,y,dx-dy);
817 while (lx>2 && x[lx-1]==0) lx--;
818 dx = F2x_degree_lg(x,lx);
819 }
820 return F2x_renormalize(x, lx);
821 }
822
823 GEN
F2x_divrem(GEN x,GEN y,GEN * pr)824 F2x_divrem(GEN x, GEN y, GEN *pr)
825 {
826 long dx, dy, dz, lx = lg(x), vs = x[1];
827 GEN z;
828
829 dy = F2x_degree(y);
830 if (dy<0) pari_err_INV("F2x_divrem",y);
831 if (pr == ONLY_REM) return F2x_rem(x, y);
832 if (!dy)
833 {
834 z = F2x_copy(x);
835 if (pr && pr != ONLY_DIVIDES) *pr = pol0_F2x(vs);
836 return z;
837 }
838 dx = F2x_degree_lg(x,lx);
839 dz = dx-dy;
840 if (dz < 0)
841 {
842 if (pr == ONLY_DIVIDES) return dx < 0? F2x_copy(x): NULL;
843 z = pol0_F2x(vs);
844 if (pr) *pr = F2x_copy(x);
845 return z;
846 }
847 z = zero_zv(lg(x)-lg(y)+2); z[1] = vs;
848 x = F2x_copy(x);
849 while (dx>=dy)
850 {
851 F2x_set(z,dx-dy);
852 F2x_addshiftip(x,y,dx-dy);
853 while (lx>2 && x[lx-1]==0) lx--;
854 dx = F2x_degree_lg(x,lx);
855 }
856 z = F2x_renormalize(z, lg(z));
857 if (!pr) { cgiv(x); return z; }
858 x = F2x_renormalize(x, lx);
859 if (pr == ONLY_DIVIDES) {
860 if (lg(x) == 2) { cgiv(x); return z; }
861 return gc_NULL((pari_sp)(z + lg(z)));
862 }
863 *pr = x; return z;
864 }
865
866 long
F2x_valrem(GEN x,GEN * Z)867 F2x_valrem(GEN x, GEN *Z)
868 {
869 long v, v2, i, l=lg(x);
870 GEN y;
871 if (l==2) { *Z = F2x_copy(x); return LONG_MAX; }
872 for (i=2; i<l && x[i]==0; i++) /*empty*/;
873 v = i-2;
874 v2 = (i < l)? vals(x[i]): 0;
875 if (v+v2 == 0) { *Z = x; return 0; }
876 l -= i-2;
877 y = cgetg(l, t_VECSMALL); y[1] = x[1];
878 if (v2 == 0)
879 for (i=2; i<l; i++) y[i] = x[i+v];
880 else if (l == 3)
881 y[2] = ((ulong)x[2+v]) >> v2;
882 else
883 {
884 const ulong sh = BITS_IN_LONG - v2;
885 ulong r = x[2+v];
886 for (i=3; i<l; i++)
887 {
888 y[i-1] = (x[i+v] << sh) | (r >> v2);
889 r = x[i+v];
890 }
891 y[l-1] = r >> v2;
892 (void)F2x_renormalize(y,l);
893 }
894 *Z = y; return (v << TWOPOTBITS_IN_LONG) + v2;
895 }
896
897 GEN
F2x_deflate(GEN x,long d)898 F2x_deflate(GEN x, long d)
899 {
900 GEN y;
901 long i,id, dy, dx = F2x_degree(x);
902 if (d <= 1) return F2x_copy(x);
903 if (dx < 0) return F2x_copy(x);
904 dy = dx/d; /* dy+1 coefficients + 1 extra word for variable */
905 y = zero_zv(nbits2lg(dy+1)-1); y[1] = x[1];
906 for (i=id=0; i<=dy; i++,id+=d)
907 if (F2x_coeff(x,id)) F2x_set(y, i);
908 return y;
909 }
910
911 /* write p(X) = e(X^2) + Xo(X^2), shallow function */
912 void
F2x_even_odd(GEN p,GEN * pe,GEN * po)913 F2x_even_odd(GEN p, GEN *pe, GEN *po)
914 {
915 long n = F2x_degree(p), n0, n1, i;
916 GEN p0, p1;
917
918 if (n <= 0) { *pe = F2x_copy(p); *po = pol0_F2x(p[1]); return; }
919
920 n0 = (n>>1)+1; n1 = n+1 - n0; /* n1 <= n0 <= n1+1 */
921 p0 = zero_zv(nbits2lg(n0+1)-1); p0[1] = p[1];
922 p1 = zero_zv(nbits2lg(n1+1)-1); p1[1] = p[1];
923 for (i=0; i<n1; i++)
924 {
925 if (F2x_coeff(p,i<<1)) F2x_set(p0,i);
926 if (F2x_coeff(p,1+(i<<1))) F2x_set(p1,i);
927 }
928 if (n1 != n0 && F2x_coeff(p,i<<1)) F2x_set(p0,i);
929 *pe = F2x_renormalize(p0,lg(p0));
930 *po = F2x_renormalize(p1,lg(p1));
931 }
932
933 GEN
F2x_deriv(GEN z)934 F2x_deriv(GEN z)
935 {
936 const ulong mask = ULONG_MAX/3UL;
937 long i,l = lg(z);
938 GEN x = cgetg(l, t_VECSMALL); x[1] = z[1];
939 for (i=2; i<l; i++) x[i] = (((ulong)z[i])>>1)&mask;
940 return F2x_renormalize(x,l);
941 }
942
943 GEN
F2x_gcd(GEN a,GEN b)944 F2x_gcd(GEN a, GEN b)
945 {
946 pari_sp av = avma;
947 if (lg(b) > lg(a)) swap(a, b);
948 while (lgpol(b))
949 {
950 GEN c = F2x_rem(a,b);
951 a = b; b = c;
952 if (gc_needed(av,2))
953 {
954 if (DEBUGMEM>1) pari_warn(warnmem,"F2x_gcd (d = %ld)",F2x_degree(c));
955 gerepileall(av,2, &a,&b);
956 }
957 }
958 if (gc_needed(av,2)) a = gerepileuptoleaf(av, a);
959 return a;
960 }
961
962 GEN
F2x_extgcd(GEN a,GEN b,GEN * ptu,GEN * ptv)963 F2x_extgcd(GEN a, GEN b, GEN *ptu, GEN *ptv)
964 {
965 pari_sp av=avma;
966 GEN u,v,d,d1,v1;
967 long vx = a[1];
968 d = a; d1 = b;
969 v = pol0_F2x(vx); v1 = pol1_F2x(vx);
970 while (lgpol(d1))
971 {
972 GEN r, q = F2x_divrem(d,d1, &r);
973 v = F2x_add(v,F2x_mul(q,v1));
974 u=v; v=v1; v1=u;
975 u=r; d=d1; d1=u;
976 if (gc_needed(av,2))
977 {
978 if (DEBUGMEM>1) pari_warn(warnmem,"F2x_extgcd (d = %ld)",F2x_degree(d));
979 gerepileall(av,5, &d,&d1,&u,&v,&v1);
980 }
981 }
982 if (ptu) *ptu = F2x_div(F2x_add(d, F2x_mul(b,v)), a);
983 *ptv = v;
984 if (gc_needed(av,2)) gerepileall(av,ptu?3:2,&d,ptv,ptu);
985 return d;
986 }
987
988 static GEN
F2x_halfgcd_i(GEN a,GEN b)989 F2x_halfgcd_i(GEN a, GEN b)
990 {
991 pari_sp av=avma;
992 GEN u,u1,v,v1;
993 long vx = a[1];
994 long n = (F2x_degree(a)+1)>>1;
995 u1 = v = pol0_F2x(vx);
996 u = v1 = pol1_F2x(vx);
997 while (F2x_degree(b)>=n)
998 {
999 GEN r, q = F2x_divrem(a,b, &r);
1000 a = b; b = r; swap(u,u1); swap(v,v1);
1001 u1 = F2x_add(u1, F2x_mul(u, q));
1002 v1 = F2x_add(v1, F2x_mul(v, q));
1003 if (gc_needed(av,2))
1004 {
1005 if (DEBUGMEM>1) pari_warn(warnmem,"F2x_halfgcd (d = %ld)",F2x_degree(b));
1006 gerepileall(av,6, &a,&b,&u1,&v1,&u,&v);
1007 }
1008 }
1009 return gerepilecopy(av, mkmat2(mkcol2(u,u1), mkcol2(v,v1)));
1010 }
1011
1012 GEN
F2x_halfgcd(GEN x,GEN y)1013 F2x_halfgcd(GEN x, GEN y)
1014 {
1015 pari_sp av;
1016 GEN M,q,r;
1017 if (F2x_degree(y)<F2x_degree(x)) return F2x_halfgcd_i(x,y);
1018 av = avma;
1019 q = F2x_divrem(y,x,&r);
1020 M = F2x_halfgcd_i(x,r);
1021 gcoeff(M,1,1) = F2x_add(gcoeff(M,1,1), F2x_mul(q, gcoeff(M,1,2)));
1022 gcoeff(M,2,1) = F2x_add(gcoeff(M,2,1), F2x_mul(q, gcoeff(M,2,2)));
1023 return gerepilecopy(av, M);
1024 }
1025
1026 GEN
F2xq_mul(GEN x,GEN y,GEN pol)1027 F2xq_mul(GEN x,GEN y,GEN pol)
1028 {
1029 GEN z = F2x_mul(x,y);
1030 return F2x_rem(z,pol);
1031 }
1032
1033 GEN
F2xq_sqr(GEN x,GEN pol)1034 F2xq_sqr(GEN x,GEN pol)
1035 {
1036 GEN z = F2x_sqr(x);
1037 return F2x_rem(z,pol);
1038 }
1039
1040 GEN
F2xq_invsafe(GEN x,GEN T)1041 F2xq_invsafe(GEN x, GEN T)
1042 {
1043 GEN V, z = F2x_extgcd(get_F2x_mod(T), x, NULL, &V);
1044 if (F2x_degree(z)) return NULL;
1045 return V;
1046 }
1047
1048 GEN
F2xq_inv(GEN x,GEN T)1049 F2xq_inv(GEN x,GEN T)
1050 {
1051 pari_sp av=avma;
1052 GEN U = F2xq_invsafe(x, T);
1053 if (!U) pari_err_INV("F2xq_inv", F2x_to_ZX(x));
1054 return gerepileuptoleaf(av, U);
1055 }
1056
1057 GEN
F2xq_div(GEN x,GEN y,GEN T)1058 F2xq_div(GEN x,GEN y,GEN T)
1059 {
1060 pari_sp av = avma;
1061 return gerepileuptoleaf(av, F2xq_mul(x,F2xq_inv(y,T),T));
1062 }
1063
1064 static GEN
_F2xq_red(void * E,GEN x)1065 _F2xq_red(void *E, GEN x) { return F2x_rem(x, (GEN)E); }
1066 static GEN
_F2xq_add(void * E,GEN x,GEN y)1067 _F2xq_add(void *E, GEN x, GEN y) { (void)E; return F2x_add(x,y); }
1068
1069 static GEN
_F2xq_cmul(void * E,GEN P,long a,GEN x)1070 _F2xq_cmul(void *E, GEN P, long a, GEN x)
1071 {
1072 GEN pol = (GEN) E;
1073 return F2x_coeff(P,a) ? x: pol0_F2x(pol[1]);
1074 }
1075 static GEN
_F2xq_sqr(void * E,GEN x)1076 _F2xq_sqr(void *E, GEN x) { return F2xq_sqr(x, (GEN) E); }
1077 static GEN
_F2xq_mul(void * E,GEN x,GEN y)1078 _F2xq_mul(void *E, GEN x, GEN y) { return F2xq_mul(x,y, (GEN) E); }
1079
1080 static GEN
_F2xq_one(void * E)1081 _F2xq_one(void *E)
1082 {
1083 GEN pol = (GEN) E;
1084 return pol1_F2x(pol[1]);
1085 }
1086 static GEN
_F2xq_zero(void * E)1087 _F2xq_zero(void *E)
1088 {
1089 GEN pol = (GEN) E;
1090 return pol0_F2x(pol[1]);
1091 }
1092
1093 GEN
F2xq_pow(GEN x,GEN n,GEN pol)1094 F2xq_pow(GEN x, GEN n, GEN pol)
1095 {
1096 pari_sp av=avma;
1097 GEN y;
1098
1099 if (!signe(n)) return pol1_F2x(x[1]);
1100 if (is_pm1(n)) /* +/- 1 */
1101 return (signe(n) < 0)? F2xq_inv(x,pol): F2x_copy(x);
1102
1103 if (signe(n) < 0) x = F2xq_inv(x,pol);
1104 y = gen_pow_i(x, n, (void*)pol, &_F2xq_sqr, &_F2xq_mul);
1105 return gerepilecopy(av, y);
1106 }
1107
1108 GEN
F2xq_powu(GEN x,ulong n,GEN pol)1109 F2xq_powu(GEN x, ulong n, GEN pol)
1110 {
1111 pari_sp av=avma;
1112 GEN y;
1113 switch(n)
1114 {
1115 case 0: return pol1_F2x(x[1]);
1116 case 1: return F2x_copy(x);
1117 case 2: return F2xq_sqr(x,pol);
1118 }
1119 y = gen_powu_i(x, n, (void*)pol, &_F2xq_sqr, &_F2xq_mul);
1120 return gerepilecopy(av, y);
1121 }
1122
1123 GEN
F2xq_pow_init(GEN x,GEN n,long k,GEN T)1124 F2xq_pow_init(GEN x, GEN n, long k, GEN T)
1125 {
1126 return gen_pow_init(x, n, k, (void*)T, &_F2xq_sqr, &_F2xq_mul);
1127 }
1128
1129 GEN
F2xq_pow_table(GEN R,GEN n,GEN T)1130 F2xq_pow_table(GEN R, GEN n, GEN T)
1131 {
1132 return gen_pow_table(R, n, (void*)T, &_F2xq_one, &_F2xq_mul);
1133 }
1134
1135 /* generates the list of powers of x of degree 0,1,2,...,l*/
1136 GEN
F2xq_powers(GEN x,long l,GEN T)1137 F2xq_powers(GEN x, long l, GEN T)
1138 {
1139 int use_sqr = 2*F2x_degree(x) >= get_F2x_degree(T);
1140 return gen_powers(x, l, use_sqr, (void*)T, &_F2xq_sqr, &_F2xq_mul, &_F2xq_one);
1141 }
1142
1143 GEN
F2xq_matrix_pow(GEN y,long n,long m,GEN P)1144 F2xq_matrix_pow(GEN y, long n, long m, GEN P)
1145 {
1146 return F2xV_to_F2m(F2xq_powers(y,m-1,P),n);
1147 }
1148
1149 GEN
F2x_Frobenius(GEN T)1150 F2x_Frobenius(GEN T)
1151 {
1152 return F2xq_sqr(polx_F2x(get_F2x_var(T)), T);
1153 }
1154
1155 GEN
F2x_matFrobenius(GEN T)1156 F2x_matFrobenius(GEN T)
1157 {
1158 long n = get_F2x_degree(T);
1159 return F2xq_matrix_pow(F2x_Frobenius(T), n, n, T);
1160 }
1161
1162 static struct bb_algebra F2xq_algebra = { _F2xq_red, _F2xq_add, _F2xq_add,
1163 _F2xq_mul, _F2xq_sqr, _F2xq_one, _F2xq_zero};
1164
1165 GEN
F2x_F2xqV_eval(GEN Q,GEN x,GEN T)1166 F2x_F2xqV_eval(GEN Q, GEN x, GEN T)
1167 {
1168 long d = F2x_degree(Q);
1169 return gen_bkeval_powers(Q,d,x,(void*)T,&F2xq_algebra,_F2xq_cmul);
1170 }
1171
1172 GEN
F2x_F2xq_eval(GEN Q,GEN x,GEN T)1173 F2x_F2xq_eval(GEN Q, GEN x, GEN T)
1174 {
1175 long d = F2x_degree(Q);
1176 int use_sqr = 2*F2x_degree(x) >= get_F2x_degree(T);
1177 return gen_bkeval(Q, d, x, use_sqr, (void*)T, &F2xq_algebra, _F2xq_cmul);
1178 }
1179
1180 static GEN
F2xq_autpow_sqr(void * T,GEN x)1181 F2xq_autpow_sqr(void * T, GEN x) { return F2x_F2xq_eval(x, x, (GEN) T); }
1182
1183 static GEN
F2xq_autpow_mul(void * T,GEN x,GEN y)1184 F2xq_autpow_mul(void * T, GEN x, GEN y) { return F2x_F2xq_eval(x, y, (GEN) T); }
1185
1186 GEN
F2xq_autpow(GEN x,long n,GEN T)1187 F2xq_autpow(GEN x, long n, GEN T)
1188 {
1189 if (n==0) return F2x_rem(polx_F2x(x[1]), T);
1190 if (n==1) return F2x_rem(x, T);
1191 return gen_powu(x,n,(void*)T,F2xq_autpow_sqr,F2xq_autpow_mul);
1192 }
1193
1194 ulong
F2xq_trace(GEN x,GEN T)1195 F2xq_trace(GEN x, GEN T)
1196 {
1197 pari_sp av = avma;
1198 long n = get_F2x_degree(T)-1;
1199 GEN z = F2xq_mul(x, F2x_deriv(get_F2x_mod(T)), T);
1200 return gc_ulong(av, F2x_degree(z) < n ? 0 : 1);
1201 }
1202
1203 GEN
F2xq_conjvec(GEN x,GEN T)1204 F2xq_conjvec(GEN x, GEN T)
1205 {
1206 long i, l = 1+get_F2x_degree(T);
1207 GEN z = cgetg(l,t_COL);
1208 gel(z,1) = F2x_copy(x);
1209 for (i=2; i<l; i++) gel(z,i) = F2xq_sqr(gel(z,i-1), T);
1210 return z;
1211 }
1212
1213 static GEN
_F2xq_pow(void * data,GEN x,GEN n)1214 _F2xq_pow(void *data, GEN x, GEN n)
1215 {
1216 GEN pol = (GEN) data;
1217 return F2xq_pow(x,n, pol);
1218 }
1219
1220 static GEN
_F2xq_rand(void * data)1221 _F2xq_rand(void *data)
1222 {
1223 pari_sp av=avma;
1224 GEN pol = (GEN) data;
1225 long d = F2x_degree(pol);
1226 GEN z;
1227 do
1228 {
1229 set_avma(av);
1230 z = random_F2x(d,pol[1]);
1231 } while (lgpol(z)==0);
1232 return z;
1233 }
1234
1235 static GEN F2xq_easylog(void* E, GEN a, GEN g, GEN ord);
1236
1237 static const struct bb_group F2xq_star={_F2xq_mul,_F2xq_pow,_F2xq_rand,hash_GEN,F2x_equal,F2x_equal1,F2xq_easylog};
1238
1239 GEN
F2xq_order(GEN a,GEN ord,GEN T)1240 F2xq_order(GEN a, GEN ord, GEN T)
1241 {
1242 return gen_order(a,ord,(void*)T,&F2xq_star);
1243 }
1244
1245 static long
F2x_is_smooth_squarefree(GEN f,long r)1246 F2x_is_smooth_squarefree(GEN f, long r)
1247 {
1248 pari_sp av = avma;
1249 long i, df = F2x_degree(f);
1250 GEN sx, a;
1251 if (!df) return 1;
1252 a = sx = polx_F2x(f[1]);
1253 for(i = 1;; i++)
1254 {
1255 long dg;
1256 GEN g;
1257 a = F2xq_sqr(a, f);
1258 if (F2x_equal(a, sx)) return gc_long(av,1);
1259 if (i==r) return gc_long(av,0);
1260 g = F2x_gcd(f, F2x_add(a,sx));
1261 dg = F2x_degree(g);
1262 if (dg == df) return gc_long(av,1);
1263 if (dg) { f = F2x_div(f, g); df -= dg; a = F2x_rem(a, f); }
1264 }
1265 }
1266
1267 static long
F2x_is_smooth(GEN g,long r)1268 F2x_is_smooth(GEN g, long r)
1269 {
1270 if (lgpol(g)==0) return 0;
1271 while (1)
1272 {
1273 GEN f = F2x_gcd(g, F2x_deriv(g));
1274 if (!F2x_is_smooth_squarefree(F2x_div(g, f), r)) return 0;
1275 if (F2x_degree(f)==0) return 1;
1276 g = F2x_issquare(f) ? F2x_sqrt(f): f;
1277 }
1278 }
1279
1280 static GEN
F2x_factorel(GEN h)1281 F2x_factorel(GEN h)
1282 {
1283 GEN F = F2x_factor(h);
1284 GEN F1 = gel(F, 1), F2 = gel(F, 2);
1285 long i, l1 = lg(F1)-1;
1286 GEN p2 = cgetg(l1+1, t_VECSMALL);
1287 GEN e2 = cgetg(l1+1, t_VECSMALL);
1288 for (i = 1; i <= l1; ++i)
1289 {
1290 p2[i] = mael(F1, i, 2);
1291 e2[i] = F2[i];
1292 }
1293 return mkmat2(p2, e2);
1294 }
1295
1296 static GEN
mkF2(ulong x,long v)1297 mkF2(ulong x, long v) { return mkvecsmall2(v, x); }
1298
1299 static GEN F2xq_log_Coppersmith_d(GEN W, GEN g, long r, long n, GEN T, GEN mo);
1300
1301 static GEN
F2xq_log_from_rel(GEN W,GEN rel,long r,long n,GEN T,GEN m)1302 F2xq_log_from_rel(GEN W, GEN rel, long r, long n, GEN T, GEN m)
1303 {
1304 pari_sp av = avma;
1305 long vT = get_F2x_var(T);
1306 GEN F = gel(rel,1), E = gel(rel,2), o = gen_0;
1307 long i, l = lg(F);
1308 for(i=1; i<l; i++)
1309 {
1310 GEN R = gel(W, F[i]);
1311 if (signe(R)==0) /* Already failed */
1312 return NULL;
1313 else if (signe(R)<0) /* Not yet tested */
1314 {
1315 setsigne(gel(W,F[i]),0);
1316 R = F2xq_log_Coppersmith_d(W, mkF2(F[i],vT), r, n, T, m);
1317 if (!R) return NULL;
1318 }
1319 o = Fp_add(o, mulis(R, E[i]), m);
1320 }
1321 return gerepileuptoint(av, o);
1322 }
1323
1324 static GEN
F2xq_log_Coppersmith_d(GEN W,GEN g,long r,long n,GEN T,GEN mo)1325 F2xq_log_Coppersmith_d(GEN W, GEN g, long r, long n, GEN T, GEN mo)
1326 {
1327 pari_sp av = avma, av2;
1328 long dT = get_F2x_degree(T), vT = get_F2x_var(T);
1329 long dg = F2x_degree(g), k = r-1, m = maxss((dg-k)/2,0);
1330 long i, j, l = dg-m, N;
1331 GEN v = cgetg(k+m+1,t_MAT);
1332 long h = dT>>n, d = dT-(h<<n);
1333 GEN p1 = pol1_F2x(vT);
1334 GEN R = F2x_add(F2x_shift(p1, dT), T);
1335 GEN z = F2x_rem(F2x_shift(p1, h), g);
1336 for(i=1; i<=k+m; i++)
1337 {
1338 gel(v,i) = F2x_to_F2v(F2x_shift(z,-l),m);
1339 z = F2x_rem(F2x_shift(z,1),g);
1340 }
1341 v = F2m_ker(v);
1342 for(i=1; i<=k; i++)
1343 gel(v,i) = F2v_to_F2x(gel(v,i),vT);
1344 N = 1<<k;
1345 av2 = avma;
1346 for (i=1; i<N; i++)
1347 {
1348 GEN p,q,qh,a,b;
1349 set_avma(av2);
1350 q = pol0_F2x(vT);
1351 for(j=0; j<k; j++)
1352 if (i&(1UL<<j))
1353 q = F2x_add(q, gel(v,j+1));
1354 qh= F2x_shift(q,h);
1355 p = F2x_rem(qh,g);
1356 b = F2x_add(F2x_mul(R, F2x_pow2n(q, n)), F2x_shift(F2x_pow2n(p, n), d));
1357 if (lgpol(b)==0 || !F2x_is_smooth(b, r)) continue;
1358 a = F2x_div(F2x_add(qh,p),g);
1359 if (F2x_degree(F2x_gcd(a,q)) && F2x_degree(F2x_gcd(a,p))) continue;
1360 if (!(lgpol(a)==0 || !F2x_is_smooth(a, r)))
1361 {
1362 GEN F = F2x_factorel(b);
1363 GEN G = F2x_factorel(a);
1364 GEN FG = vecsmall_concat(vecsmall_append(gel(F, 1), 2), gel(G, 1));
1365 GEN E = vecsmall_concat(vecsmall_append(gel(F, 2), -d),
1366 zv_z_mul(gel(G, 2),-(1L<<n)));
1367 GEN R = famatsmall_reduce(mkmat2(FG, E));
1368 GEN l = F2xq_log_from_rel(W, R, r, n, T, mo);
1369 if (!l) continue;
1370 l = Fp_div(l,int2n(n),mo);
1371 if (dg <= r)
1372 {
1373 affii(l,gel(W,g[2]));
1374 if (DEBUGLEVEL>1) err_printf("Found %lu\n", g[2]);
1375 }
1376 return gerepileuptoint(av, l);
1377 }
1378 }
1379 return gc_NULL(av);
1380 }
1381
1382 static GEN
F2xq_log_find_rel(GEN b,long r,GEN T,GEN * g,ulong * e)1383 F2xq_log_find_rel(GEN b, long r, GEN T, GEN *g, ulong *e)
1384 {
1385 pari_sp av = avma;
1386 while (1)
1387 {
1388 GEN M;
1389 *g = F2xq_mul(*g, b, T); (*e)++;
1390 M = F2x_halfgcd(*g,T);
1391 if (F2x_is_smooth(gcoeff(M,1,1), r))
1392 {
1393 GEN z = F2x_add(F2x_mul(gcoeff(M,1,1),*g), F2x_mul(gcoeff(M,1,2),T));
1394 if (F2x_is_smooth(z, r))
1395 {
1396 GEN F = F2x_factorel(z);
1397 GEN G = F2x_factorel(gcoeff(M,1,1));
1398 GEN rel = mkmat2(vecsmall_concat(gel(F, 1),gel(G, 1)),
1399 vecsmall_concat(gel(F, 2),zv_neg(gel(G, 2))));
1400 gerepileall(av, 2, g, &rel);
1401 return rel;
1402 }
1403 }
1404 if (gc_needed(av,2))
1405 {
1406 if (DEBUGMEM>1) pari_warn(warnmem,"F2xq_log_find_rel");
1407 *g = gerepileuptoleaf(av, *g);
1408 }
1409 }
1410 }
1411
1412 static GEN
F2xq_log_Coppersmith_rec(GEN W,long r2,GEN a,long r,long n,GEN T,GEN m)1413 F2xq_log_Coppersmith_rec(GEN W, long r2, GEN a, long r, long n, GEN T, GEN m)
1414 {
1415 long vT = get_F2x_var(T);
1416 GEN b = polx_F2x(vT);
1417 ulong AV = 0;
1418 GEN g = a, bad = pol0_F2x(vT);
1419 pari_timer ti;
1420 while(1)
1421 {
1422 long i, l;
1423 GEN V, F, E, Ao;
1424 timer_start(&ti);
1425 V = F2xq_log_find_rel(b, r2, T, &g, &AV);
1426 if (DEBUGLEVEL>1) timer_printf(&ti,"%ld-smooth element",r2);
1427 F = gel(V,1); E = gel(V,2);
1428 l = lg(F);
1429 Ao = gen_0;
1430 for(i=1; i<l; i++)
1431 {
1432 GEN Fi = mkF2(F[i], vT);
1433 GEN R;
1434 if (F2x_degree(Fi) <= r)
1435 {
1436 if (signe(gel(W,F[i]))==0)
1437 break;
1438 else if (signe(gel(W,F[i]))<0)
1439 {
1440 setsigne(gel(W,F[i]),0);
1441 R = F2xq_log_Coppersmith_d(W,Fi,r,n,T,m);
1442 } else
1443 R = gel(W,F[i]);
1444 }
1445 else
1446 {
1447 if (F2x_equal(Fi,bad)) break;
1448 R = F2xq_log_Coppersmith_d(W,Fi,r,n,T,m);
1449 if (!R) bad = Fi;
1450 }
1451 if (!R) break;
1452 Ao = Fp_add(Ao, mulis(R, E[i]), m);
1453 }
1454 if (i==l) return subiu(Ao,AV);
1455 }
1456 }
1457
1458 /* Coppersmith:
1459 T*X^e = X^(h*2^n)-R
1460 (u*x^h + v)^(2^n) = u^(2^n)*X^(h*2^n)+v^(2^n)
1461 (u*x^h + v)^(2^n) = u^(2^n)*R+v^(2^n)
1462 */
1463
1464 static GEN
rel_Coppersmith(GEN u,GEN v,long h,GEN R,long r,long n,long d)1465 rel_Coppersmith(GEN u, GEN v, long h, GEN R, long r, long n, long d)
1466 {
1467 GEN b, F, G, M;
1468 GEN a = F2x_add(F2x_shift(u, h), v);
1469 if (!F2x_is_smooth(a, r)) return NULL;
1470 b = F2x_add(F2x_mul(R, F2x_pow2n(u, n)), F2x_shift(F2x_pow2n(v, n),d));
1471 if (!F2x_is_smooth(b, r)) return NULL;
1472 F = F2x_factorel(a);
1473 G = F2x_factorel(b);
1474 M = mkmat2(vecsmall_concat(gel(F, 1), vecsmall_append(gel(G, 1), 2)),
1475 vecsmall_concat(zv_z_mul(gel(F, 2),1UL<<n), vecsmall_append(zv_neg(gel(G, 2)),d)));
1476 return famatsmall_reduce(M);
1477 }
1478
1479 GEN
F2xq_log_Coppersmith_worker(GEN u,long i,GEN V,GEN R)1480 F2xq_log_Coppersmith_worker(GEN u, long i, GEN V, GEN R)
1481 {
1482 long r = V[1], h = V[2], n = V[3], d = V[4];
1483 pari_sp ltop = avma;
1484 GEN v = mkF2(0,u[1]);
1485 GEN L = cgetg(2*i+1, t_VEC);
1486 pari_sp av = avma;
1487 long j;
1488 long nbtest=0, rel = 1;
1489 for(j=1; j<=i; j++)
1490 {
1491 v[2] = j;
1492 set_avma(av);
1493 if (F2x_degree(F2x_gcd(u,v))==0)
1494 {
1495 GEN z = rel_Coppersmith(u, v, h, R, r, n, d);
1496 nbtest++;
1497 if (z) { gel(L, rel++) = z; av = avma; }
1498 if (i==j) continue;
1499 z = rel_Coppersmith(v, u, h, R, r, n, d);
1500 nbtest++;
1501 if (z) { gel(L, rel++) = z; av = avma; }
1502 }
1503 }
1504 setlg(L,rel);
1505 return gerepilecopy(ltop, mkvec2(stoi(nbtest), L));
1506 }
1507
1508 static GEN
F2xq_log_Coppersmith(long nbrel,long r,long n,GEN T)1509 F2xq_log_Coppersmith(long nbrel, long r, long n, GEN T)
1510 {
1511 long dT = get_F2x_degree(T), vT = get_F2x_var(T);
1512 long h = dT>>n, d = dT-(h<<n);
1513 GEN R = F2x_add(F2x_shift(pol1_F2x(vT), dT), T);
1514 GEN u = mkF2(0,vT);
1515 long rel = 1, nbtest = 0;
1516 GEN M = cgetg(nbrel+1, t_VEC);
1517 long i = 0;
1518 GEN worker = snm_closure(is_entry("_F2xq_log_Coppersmith_worker"),
1519 mkvec2(mkvecsmall4(r, h, n, d), R));
1520 struct pari_mt pt;
1521 long running, pending = 0, stop=0;
1522 mt_queue_start(&pt, worker);
1523 if (DEBUGLEVEL) err_printf("Coppersmith (R = %ld): ",F2x_degree(R));
1524 while ((running = !stop) || pending)
1525 {
1526 GEN L, done;
1527 long j, l;
1528 u[2] = i;
1529 mt_queue_submit(&pt, 0, running ? mkvec2(u, stoi(i)): NULL);
1530 done = mt_queue_get(&pt, NULL, &pending);
1531 if (!done) continue;
1532 L = gel(done, 2); nbtest += itos(gel(done,1));
1533 l = lg(L);
1534 if (l > 1)
1535 {
1536 for (j=1; j<l; j++)
1537 {
1538 if (rel>nbrel) break;
1539 gel(M,rel++) = gel(L,j);
1540 if (DEBUGLEVEL && (rel&511UL)==0)
1541 err_printf("%ld%%[%ld] ",rel*100/nbrel,i);
1542 }
1543 }
1544 if (rel>nbrel) stop=1;
1545 i++;
1546 }
1547 mt_queue_end(&pt);
1548 if (DEBUGLEVEL) err_printf(": %ld tests\n", nbtest);
1549 return M;
1550 }
1551
1552 static GEN
smallirred_F2x(ulong n,long sv)1553 smallirred_F2x(ulong n, long sv)
1554 {
1555 GEN a = zero_zv(nbits2lg(n+1)-1);
1556 a[1] = sv; F2x_set(a,n); a[2]++;
1557 while (!F2x_is_irred(a)) a[2]+=2;
1558 return a;
1559 }
1560
1561 static GEN
check_kernel(long N,GEN M,long nbi,GEN T,GEN m)1562 check_kernel(long N, GEN M, long nbi, GEN T, GEN m)
1563 {
1564 pari_sp av = avma;
1565 long dT = get_F2x_degree(T), vT = get_F2x_var(T);
1566 GEN K = FpMs_leftkernel_elt(M, N, m);
1567 long i, f=0, tbs;
1568 long l = lg(K), lm = lgefint(m);
1569 GEN idx = diviiexact(int2um1(dT), m);
1570 GEN g = F2xq_pow(polx_F2x(vT), idx, T);
1571 GEN tab;
1572 pari_timer ti;
1573 if (DEBUGLEVEL) timer_start(&ti);
1574 K = FpC_Fp_mul(K, Fp_inv(gel(K,2), m), m);
1575 tbs = maxss(1, expu(nbi/expi(m)));
1576 tab = F2xq_pow_init(g, int2n(dT), tbs, T);
1577 for(i=1; i<l; i++)
1578 {
1579 GEN k = gel(K,i);
1580 if (signe(k)==0 || !F2x_equal(F2xq_pow_table(tab, k, T),
1581 F2xq_pow(mkF2(i,vT), idx, T)))
1582 gel(K,i) = cgetineg(lm);
1583 else
1584 f++;
1585 }
1586 if (DEBUGLEVEL) timer_printf(&ti,"found %ld/%ld logs", f, nbi);
1587 return gerepileupto(av, K);
1588 }
1589
1590 static GEN
F2xq_log_index(GEN a0,GEN b0,GEN m,GEN T0)1591 F2xq_log_index(GEN a0, GEN b0, GEN m, GEN T0)
1592 {
1593 pari_sp av = avma;
1594 GEN M, S, a, b, Ao=NULL, Bo=NULL, W, e;
1595 pari_timer ti;
1596 long n = F2x_degree(T0), r = (long) (sqrt((double) 2*n))-(n>100);
1597 GEN T = smallirred_F2x(n,T0[1]);
1598 long d = 2, r2 = 3*r/2, d2 = 2;
1599 long N = (1UL<<(r+1))-1UL;
1600 long nbi = itos(ffsumnbirred(gen_2, r)), nbrel=nbi*5/4;
1601 if (DEBUGLEVEL)
1602 {
1603 err_printf("F2xq_log: Parameters r=%ld r2=%ld\n", r,r2);
1604 err_printf("F2xq_log: Size FB=%ld rel. needed=%ld\n", nbi, nbrel);
1605 timer_start(&ti);
1606 }
1607 S = Flx_to_F2x(Flx_ffisom(F2x_to_Flx(T0),F2x_to_Flx(T),2));
1608 a = F2x_F2xq_eval(a0, S, T);
1609 b = F2x_F2xq_eval(b0, S, T);
1610 if (DEBUGLEVEL) timer_printf(&ti,"model change");
1611 M = F2xq_log_Coppersmith(nbrel,r,d,T);
1612 if(DEBUGLEVEL)
1613 timer_printf(&ti,"relations");
1614 W = check_kernel(N, M, nbi, T, m);
1615 timer_start(&ti);
1616 Ao = F2xq_log_Coppersmith_rec(W, r2, a, r, d2, T, m);
1617 if (DEBUGLEVEL) timer_printf(&ti,"smooth element");
1618 Bo = F2xq_log_Coppersmith_rec(W, r2, b, r, d2, T, m);
1619 if (DEBUGLEVEL) timer_printf(&ti,"smooth generator");
1620 e = Fp_div(Ao, Bo, m);
1621 if (!F2x_equal(F2xq_pow(b0,e,T0),a0)) pari_err_BUG("F2xq_log");
1622 return gerepileupto(av, e);
1623 }
1624
1625 static GEN
F2xq_easylog(void * E,GEN a,GEN g,GEN ord)1626 F2xq_easylog(void* E, GEN a, GEN g, GEN ord)
1627 {
1628 if (F2x_equal1(a)) return gen_0;
1629 if (F2x_equal(a,g)) return gen_1;
1630 if (typ(ord)!=t_INT) return NULL;
1631 if (expi(ord)<28) return NULL;
1632 return F2xq_log_index(a,g,ord,(GEN)E);
1633 }
1634
1635 GEN
F2xq_log(GEN a,GEN g,GEN ord,GEN T)1636 F2xq_log(GEN a, GEN g, GEN ord, GEN T)
1637 {
1638 GEN z, v = get_arith_ZZM(ord);
1639 ord = mkvec2(gel(v,1),ZM_famat_limit(gel(v,2),int2n(28)));
1640 z = gen_PH_log(a,g,ord,(void*)T,&F2xq_star);
1641 return z? z: cgetg(1,t_VEC);
1642 }
1643
1644 GEN
F2xq_Artin_Schreier(GEN a,GEN T)1645 F2xq_Artin_Schreier(GEN a, GEN T)
1646 {
1647 pari_sp ltop=avma;
1648 long j,N = get_F2x_degree(T), vT = get_F2x_var(T);
1649 GEN Q = F2x_matFrobenius(T);
1650 for (j=1; j<=N; j++)
1651 F2m_flip(Q,j,j);
1652 F2v_add_inplace(gel(Q,1),a);
1653 Q = F2m_ker_sp(Q,0);
1654 if (lg(Q)!=2) return NULL;
1655 Q = gel(Q,1);
1656 Q[1] = vT;
1657 return gerepileuptoleaf(ltop, F2x_renormalize(Q, lg(Q)));
1658 }
1659
1660 GEN
F2xq_sqrt_fast(GEN c,GEN sqx,GEN T)1661 F2xq_sqrt_fast(GEN c, GEN sqx, GEN T)
1662 {
1663 GEN c0, c1;
1664 F2x_even_odd(c, &c0, &c1);
1665 return F2x_add(c0, F2xq_mul(c1, sqx, T));
1666 }
1667
1668 static int
F2x_is_x(GEN a)1669 F2x_is_x(GEN a) { return lg(a)==3 && a[2]==2; }
1670
1671 GEN
F2xq_sqrt(GEN a,GEN T)1672 F2xq_sqrt(GEN a, GEN T)
1673 {
1674 pari_sp av = avma;
1675 long n = get_F2x_degree(T), vT = get_F2x_var(T);
1676 GEN sqx;
1677 if (n==1) return F2x_copy(a);
1678 if (n==2) return F2xq_sqr(a,T);
1679 sqx = F2xq_autpow(mkF2(4, vT), n-1, T);
1680 return gerepileuptoleaf(av, F2x_is_x(a)? sqx: F2xq_sqrt_fast(a,sqx,T));
1681 }
1682
1683 GEN
F2xq_sqrtn(GEN a,GEN n,GEN T,GEN * zeta)1684 F2xq_sqrtn(GEN a, GEN n, GEN T, GEN *zeta)
1685 {
1686 long dT = get_F2x_degree(T), vT = get_F2x_var(T);
1687 if (!lgpol(a))
1688 {
1689 if (signe(n) < 0) pari_err_INV("F2xq_sqrtn",a);
1690 if (zeta)
1691 *zeta=pol1_F2x(vT);
1692 return pol0_F2x(vT);
1693 }
1694 return gen_Shanks_sqrtn(a, n, int2um1(dT), zeta, (void*)T, &F2xq_star);
1695 }
1696
1697 GEN
gener_F2xq(GEN T,GEN * po)1698 gener_F2xq(GEN T, GEN *po)
1699 {
1700 long i, j, vT = get_F2x_var(T), f = get_F2x_degree(T);
1701 pari_sp av0 = avma, av;
1702 GEN g, L2, o, q;
1703
1704 if (f == 1) {
1705 if (po) *po = mkvec2(gen_1, trivial_fact());
1706 return pol1_F2x(vT);
1707 }
1708 q = int2um1(f);
1709 o = factor_pn_1(gen_2,f);
1710 L2 = leafcopy( gel(o, 1) );
1711 for (i = j = 1; i < lg(L2); i++)
1712 {
1713 if (absequaliu(gel(L2,i),2)) continue;
1714 gel(L2,j++) = diviiexact(q, gel(L2,i));
1715 }
1716 setlg(L2, j);
1717 for (av = avma;; set_avma(av))
1718 {
1719 g = random_F2x(f, vT);
1720 if (F2x_degree(g) < 1) continue;
1721 for (i = 1; i < j; i++)
1722 {
1723 GEN a = F2xq_pow(g, gel(L2,i), T);
1724 if (F2x_equal1(a)) break;
1725 }
1726 if (i == j) break;
1727 }
1728 if (!po) g = gerepilecopy(av0, g);
1729 else {
1730 *po = mkvec2(int2um1(f), o);
1731 gerepileall(av0, 2, &g, po);
1732 }
1733 return g;
1734 }
1735
1736 static GEN
_F2xq_neg(void * E,GEN x)1737 _F2xq_neg(void *E, GEN x) { (void) E; return F2x_copy(x); }
1738 static GEN
_F2xq_rmul(void * E,GEN x,GEN y)1739 _F2xq_rmul(void *E, GEN x, GEN y) { (void) E; return F2x_mul(x,y); }
1740 static GEN
_F2xq_inv(void * E,GEN x)1741 _F2xq_inv(void *E, GEN x) { return F2xq_inv(x, (GEN) E); }
1742 static int
_F2xq_equal0(GEN x)1743 _F2xq_equal0(GEN x) { return lgpol(x)==0; }
1744 static GEN
_F2xq_s(void * E,long x)1745 _F2xq_s(void *E, long x)
1746 { GEN T = (GEN) E;
1747 long v = get_F2x_var(T);
1748 return odd(x)? pol1_F2x(v): pol0_F2x(v);
1749 }
1750
1751 static const struct bb_field F2xq_field={_F2xq_red,_F2xq_add,_F2xq_rmul,_F2xq_neg,
1752 _F2xq_inv,_F2xq_equal0,_F2xq_s};
1753
get_F2xq_field(void ** E,GEN T)1754 const struct bb_field *get_F2xq_field(void **E, GEN T)
1755 {
1756 *E = (void *) T;
1757 return &F2xq_field;
1758 }
1759
1760 /***********************************************************************/
1761 /** **/
1762 /** F2xV **/
1763 /** **/
1764 /***********************************************************************/
1765 /* F2xV are t_VEC with F2x coefficients. */
1766
1767 GEN
FlxC_to_F2xC(GEN x)1768 FlxC_to_F2xC(GEN x) { pari_APPLY_type(t_COL, Flx_to_F2x(gel(x,i))) }
1769 GEN
F2xC_to_FlxC(GEN x)1770 F2xC_to_FlxC(GEN x) { pari_APPLY_type(t_COL, F2x_to_Flx(gel(x,i))) }
1771 GEN
F2xC_to_ZXC(GEN x)1772 F2xC_to_ZXC(GEN x) { pari_APPLY_type(t_COL, F2x_to_ZX(gel(x,i))) }
1773 GEN
F2xV_to_F2m(GEN x,long n)1774 F2xV_to_F2m(GEN x, long n) { pari_APPLY_type(t_MAT, F2x_to_F2v(gel(x,i), n)) }
1775
1776 void
F2xV_to_FlxV_inplace(GEN v)1777 F2xV_to_FlxV_inplace(GEN v)
1778 {
1779 long i, l = lg(v);
1780 for(i = 1; i < l;i++) gel(v,i) = F2x_to_Flx(gel(v,i));
1781 }
1782 void
F2xV_to_ZXV_inplace(GEN v)1783 F2xV_to_ZXV_inplace(GEN v)
1784 {
1785 long i, l = lg(v);
1786 for(i = 1; i < l; i++) gel(v,i)= F2x_to_ZX(gel(v,i));
1787 }
1788
1789 /***********************************************************************/
1790 /** **/
1791 /** F2xX **/
1792 /** **/
1793 /***********************************************************************/
1794
1795 GEN
F2xX_renormalize(GEN x,long lx)1796 F2xX_renormalize(GEN /*in place*/ x, long lx)
1797 { return FlxX_renormalize(x, lx); }
1798
1799 GEN
pol1_F2xX(long v,long sv)1800 pol1_F2xX(long v, long sv) { return pol1_FlxX(v, sv); }
1801
1802 GEN
polx_F2xX(long v,long sv)1803 polx_F2xX(long v, long sv) { return polx_FlxX(v, sv); }
1804
1805 long
F2xY_degreex(GEN b)1806 F2xY_degreex(GEN b)
1807 {
1808 long deg = 0, i;
1809 if (!signe(b)) return -1;
1810 for (i = 2; i < lg(b); ++i)
1811 deg = maxss(deg, F2x_degree(gel(b, i)));
1812 return deg;
1813 }
1814
1815 GEN
FlxX_to_F2xX(GEN B)1816 FlxX_to_F2xX(GEN B)
1817 {
1818 long lb=lg(B);
1819 long i;
1820 GEN b=cgetg(lb,t_POL);
1821 b[1]=evalsigne(1)|(((ulong)B[1])&VARNBITS);
1822 for (i=2; i<lb; i++)
1823 gel(b,i) = Flx_to_F2x(gel(B,i));
1824 return F2xX_renormalize(b, lb);
1825 }
1826
1827 GEN
ZXX_to_F2xX(GEN B,long v)1828 ZXX_to_F2xX(GEN B, long v)
1829 {
1830 long lb=lg(B);
1831 long i;
1832 GEN b=cgetg(lb,t_POL);
1833 b[1]=evalsigne(1)|(((ulong)B[1])&VARNBITS);
1834 for (i=2; i<lb; i++)
1835 switch (typ(gel(B,i)))
1836 {
1837 case t_INT:
1838 gel(b,i) = Z_to_F2x(gel(B,i), evalvarn(v));
1839 break;
1840 case t_POL:
1841 gel(b,i) = ZX_to_F2x(gel(B,i));
1842 break;
1843 }
1844 return F2xX_renormalize(b, lb);
1845 }
1846
1847 GEN
F2xX_to_FlxX(GEN B)1848 F2xX_to_FlxX(GEN B)
1849 {
1850 long i, lb = lg(B);
1851 GEN b = cgetg(lb,t_POL);
1852 for (i=2; i<lb; i++)
1853 gel(b,i) = F2x_to_Flx(gel(B,i));
1854 b[1] = B[1]; return b;
1855 }
1856
1857 GEN
F2xX_to_ZXX(GEN B)1858 F2xX_to_ZXX(GEN B)
1859 {
1860 long i, lb = lg(B);
1861 GEN b = cgetg(lb,t_POL);
1862 for (i=2; i<lb; i++)
1863 {
1864 GEN c = gel(B,i);
1865 gel(b,i) = lgpol(c) ? F2x_equal1(c) ? gen_1 : F2x_to_ZX(c) : gen_0;
1866 }
1867 b[1] = B[1]; return b;
1868 }
1869
1870 GEN
F2xX_deriv(GEN z)1871 F2xX_deriv(GEN z)
1872 {
1873 long i,l = lg(z)-1;
1874 GEN x;
1875 if (l < 2) l = 2;
1876 x = cgetg(l, t_POL); x[1] = z[1];
1877 for (i=2; i<l; i++) gel(x,i) = odd(i) ? pol0_F2x(mael(z,i+1,1)): gel(z,i+1);
1878 return F2xX_renormalize(x,l);
1879 }
1880
1881 static GEN
F2xX_addspec(GEN x,GEN y,long lx,long ly)1882 F2xX_addspec(GEN x, GEN y, long lx, long ly)
1883 {
1884 long i,lz;
1885 GEN z;
1886 if (ly>lx) swapspec(x,y, lx,ly);
1887 lz = lx+2; z = cgetg(lz, t_POL);
1888 for (i=0; i<ly; i++) gel(z,i+2) = F2x_add(gel(x,i), gel(y,i));
1889 for ( ; i<lx; i++) gel(z,i+2) = F2x_copy(gel(x,i));
1890 z[1] = 0; return F2xX_renormalize(z, lz);
1891 }
1892
1893 GEN
F2xX_add(GEN x,GEN y)1894 F2xX_add(GEN x, GEN y)
1895 {
1896 long i,lz;
1897 GEN z;
1898 long lx=lg(x);
1899 long ly=lg(y);
1900 if (ly>lx) swapspec(x,y, lx,ly);
1901 lz = lx; z = cgetg(lz, t_POL); z[1]=x[1];
1902 for (i=2; i<ly; i++) gel(z,i) = F2x_add(gel(x,i), gel(y,i));
1903 for ( ; i<lx; i++) gel(z,i) = F2x_copy(gel(x,i));
1904 return F2xX_renormalize(z, lz);
1905 }
1906
1907 GEN
F2xX_F2x_add(GEN x,GEN y)1908 F2xX_F2x_add(GEN x, GEN y)
1909 {
1910 long i, lz = lg(y);
1911 GEN z;
1912 if (signe(y) == 0) return scalarpol(x, varn(y));
1913 z = cgetg(lz,t_POL); z[1] = y[1];
1914 gel(z,2) = F2x_add(gel(y,2), x);
1915 if (lz == 3) z = F2xX_renormalize(z,lz);
1916 else
1917 for(i=3;i<lz;i++) gel(z,i) = F2x_copy(gel(y,i));
1918 return z;
1919 }
1920
1921 GEN
F2xX_F2x_mul(GEN P,GEN U)1922 F2xX_F2x_mul(GEN P, GEN U)
1923 {
1924 long i, lP = lg(P);
1925 GEN res = cgetg(lP,t_POL);
1926 res[1] = P[1];
1927 for(i=2; i<lP; i++)
1928 gel(res,i) = F2x_mul(U,gel(P,i));
1929 return F2xX_renormalize(res, lP);
1930 }
1931
1932 GEN
F2xY_F2xqV_evalx(GEN P,GEN x,GEN T)1933 F2xY_F2xqV_evalx(GEN P, GEN x, GEN T)
1934 {
1935 long i, lP = lg(P);
1936 GEN res = cgetg(lP,t_POL);
1937 res[1] = P[1];
1938 for(i=2; i<lP; i++)
1939 gel(res,i) = F2x_F2xqV_eval(gel(P,i), x, T);
1940 return F2xX_renormalize(res, lP);
1941 }
1942
1943 GEN
F2xY_F2xq_evalx(GEN P,GEN x,GEN T)1944 F2xY_F2xq_evalx(GEN P, GEN x, GEN T)
1945 {
1946 pari_sp av = avma;
1947 long n = brent_kung_optpow(get_F2x_degree(T)-1,lgpol(P),1);
1948 GEN xp = F2xq_powers(x, n, T);
1949 return gerepileupto(av, F2xY_F2xqV_evalx(P, xp, T));
1950 }
1951
1952 static GEN
F2xX_to_Kronecker_spec(GEN P,long n,long d)1953 F2xX_to_Kronecker_spec(GEN P, long n, long d)
1954 {
1955 long i, k, l, N = 2*d + 1;
1956 long dP = n+1;
1957 GEN x;
1958 if (n == 0) return pol0_Flx(P[1]&VARNBITS);
1959 l = nbits2nlong(N*dP+d+1);
1960 x = zero_zv(l+1);
1961 for (k=i=0; i<n; i++, k+=N)
1962 {
1963 GEN c = gel(P,i);
1964 F2x_addshiftip(x, c, k);
1965 }
1966 x[1] = P[1]&VARNBITS; return F2x_renormalize(x, l+2);
1967 }
1968
1969 GEN
F2xX_to_Kronecker(GEN P,long d)1970 F2xX_to_Kronecker(GEN P, long d)
1971 {
1972 long i, k, l, N = 2*d + 1;
1973 long dP = degpol(P);
1974 GEN x;
1975 if (dP < 0) return pol0_Flx(P[1]&VARNBITS);
1976 l = nbits2nlong(N*dP+d+1);
1977 x = zero_zv(l+1);
1978 for (k=i=0; i<=dP; i++, k+=N)
1979 {
1980 GEN c = gel(P,i+2);
1981 F2x_addshiftip(x, c, k);
1982 }
1983 x[1] = P[1]&VARNBITS; return F2x_renormalize(x, l+2);
1984 }
1985
1986 static GEN
F2x_slice(GEN x,long n,long d)1987 F2x_slice(GEN x, long n, long d)
1988 {
1989 ulong ib, il=dvmduBIL(n, &ib);
1990 ulong db, dl=dvmduBIL(d, &db);
1991 long lN = dl+2+(db?1:0);
1992 GEN t = cgetg(lN,t_VECSMALL);
1993 t[1] = x[1];
1994 if (ib)
1995 {
1996 ulong i, ic = BITS_IN_LONG-ib;
1997 ulong r = uel(x,2+il)>>ib;
1998 for(i=0; i<dl; i++)
1999 {
2000 uel(t,2+i) = (uel(x,3+il+i)<<ic)|r;
2001 r = uel(x,3+il+i)>>ib;
2002 }
2003 if (db)
2004 uel(t,2+i) = (uel(x,3+il+i)<<ic)|r;
2005 }
2006 else
2007 {
2008 long i;
2009 for(i=2; i<lN; i++)
2010 uel(t,i) = uel(x,il+i);
2011 }
2012 if (db) uel(t,lN-1) &= (1UL<<db)-1;
2013 return F2x_renormalize(t, lN);
2014 }
2015
2016 GEN
Kronecker_to_F2xqX(GEN z,GEN T)2017 Kronecker_to_F2xqX(GEN z, GEN T)
2018 {
2019 long lz = F2x_degree(z)+1;
2020 long i, j, N = get_F2x_degree(T)*2 + 1;
2021 long lx = lz / (N-2);
2022 GEN x = cgetg(lx+3,t_POL);
2023 x[1] = z[1];
2024 for (i=0, j=2; i<lz; i+=N, j++)
2025 {
2026 GEN t = F2x_slice(z,i,minss(lz-i,N));
2027 t[1] = T[1];
2028 gel(x,j) = F2x_rem(t, T);
2029 }
2030 return F2xX_renormalize(x, j);
2031 }
2032
2033 GEN
F2xX_to_F2xC(GEN x,long N,long sv)2034 F2xX_to_F2xC(GEN x, long N, long sv)
2035 {
2036 long i, l;
2037 GEN z;
2038 l = lg(x)-1; x++;
2039 if (l > N+1) l = N+1; /* truncate higher degree terms */
2040 z = cgetg(N+1,t_COL);
2041 for (i=1; i<l ; i++) gel(z,i) = gel(x,i);
2042 for ( ; i<=N; i++) gel(z,i) = pol0_F2x(sv);
2043 return z;
2044 }
2045
2046 GEN
F2xXV_to_F2xM(GEN v,long n,long sv)2047 F2xXV_to_F2xM(GEN v, long n, long sv)
2048 {
2049 long j, N = lg(v);
2050 GEN y = cgetg(N, t_MAT);
2051 for (j=1; j<N; j++) gel(y,j) = F2xX_to_F2xC(gel(v,j), n, sv);
2052 return y;
2053 }
2054
2055 /***********************************************************************/
2056 /** **/
2057 /** F2xXV/F2xXC **/
2058 /** **/
2059 /***********************************************************************/
2060
2061 GEN
FlxXC_to_F2xXC(GEN x)2062 FlxXC_to_F2xXC(GEN x) { pari_APPLY_type(t_COL, FlxX_to_F2xX(gel(x,i))); }
2063 GEN
F2xXC_to_ZXXC(GEN x)2064 F2xXC_to_ZXXC(GEN x) { pari_APPLY_type(t_COL, F2xX_to_ZXX(gel(x,i))); }
2065
2066 /***********************************************************************/
2067 /** **/
2068 /** F2xqX **/
2069 /** **/
2070 /***********************************************************************/
2071
2072 static GEN
get_F2xqX_red(GEN T,GEN * B)2073 get_F2xqX_red(GEN T, GEN *B)
2074 {
2075 if (typ(T)!=t_VEC) { *B=NULL; return T; }
2076 *B = gel(T,1); return gel(T,2);
2077 }
2078
2079 GEN
random_F2xqX(long d1,long v,GEN T)2080 random_F2xqX(long d1, long v, GEN T)
2081 {
2082 long dT = get_F2x_degree(T), vT = get_F2x_var(T);
2083 long i, d = d1+2;
2084 GEN y = cgetg(d,t_POL); y[1] = evalsigne(1) | evalvarn(v);
2085 for (i=2; i<d; i++) gel(y,i) = random_F2x(dT, vT);
2086 return FlxX_renormalize(y,d);
2087 }
2088
2089 GEN
F2xqX_red(GEN z,GEN T)2090 F2xqX_red(GEN z, GEN T)
2091 {
2092 GEN res;
2093 long i, l = lg(z);
2094 res = cgetg(l,t_POL); res[1] = z[1];
2095 for(i=2;i<l;i++) gel(res,i) = F2x_rem(gel(z,i),T);
2096 return F2xX_renormalize(res,l);
2097 }
2098
2099 GEN
F2xqX_F2xq_mul(GEN P,GEN U,GEN T)2100 F2xqX_F2xq_mul(GEN P, GEN U, GEN T)
2101 {
2102 long i, lP = lg(P);
2103 GEN res = cgetg(lP,t_POL);
2104 res[1] = P[1];
2105 for(i=2; i<lP; i++)
2106 gel(res,i) = F2xq_mul(U,gel(P,i), T);
2107 return F2xX_renormalize(res, lP);
2108 }
2109
2110 GEN
F2xqX_F2xq_mul_to_monic(GEN P,GEN U,GEN T)2111 F2xqX_F2xq_mul_to_monic(GEN P, GEN U, GEN T)
2112 {
2113 long i, lP = lg(P);
2114 GEN res = cgetg(lP,t_POL);
2115 res[1] = P[1];
2116 for(i=2; i<lP-1; i++) gel(res,i) = F2xq_mul(U,gel(P,i), T);
2117 gel(res,lP-1) = pol1_F2x(T[1]);
2118 return F2xX_renormalize(res, lP);
2119 }
2120
2121 GEN
F2xqX_normalize(GEN z,GEN T)2122 F2xqX_normalize(GEN z, GEN T)
2123 {
2124 GEN p1 = leading_coeff(z);
2125 if (!lgpol(z) || (!degpol(p1) && p1[1] == 1)) return z;
2126 return F2xqX_F2xq_mul_to_monic(z, F2xq_inv(p1,T), T);
2127 }
2128
2129 GEN
F2xqX_mul(GEN x,GEN y,GEN T)2130 F2xqX_mul(GEN x, GEN y, GEN T)
2131 {
2132 pari_sp ltop=avma;
2133 GEN z, kx, ky;
2134 long d = get_F2x_degree(T);
2135 kx= F2xX_to_Kronecker(x, d);
2136 ky= F2xX_to_Kronecker(y, d);
2137 z = F2x_mul(ky, kx);
2138 z = Kronecker_to_F2xqX(z, T);
2139 return gerepileupto(ltop, z);
2140 }
2141
2142 static GEN
F2xqX_mulspec(GEN x,GEN y,GEN T,long nx,long ny)2143 F2xqX_mulspec(GEN x, GEN y, GEN T, long nx, long ny)
2144 {
2145 pari_sp ltop=avma;
2146 GEN z, kx, ky;
2147 long dT = get_F2x_degree(T);
2148 kx= F2xX_to_Kronecker_spec(x, nx, dT);
2149 ky= F2xX_to_Kronecker_spec(y, ny, dT);
2150 z = F2x_mul(ky, kx);
2151 z = Kronecker_to_F2xqX(z,T);
2152 return gerepileupto(ltop,z);
2153 }
2154
2155 GEN
F2xqX_sqr(GEN x,GEN T)2156 F2xqX_sqr(GEN x, GEN T)
2157 {
2158 long d = degpol(x), l = 2*d+3;
2159 GEN z;
2160 if (!signe(x)) return pol_0(varn(x));
2161 z = cgetg(l,t_POL);
2162 z[1] = x[1];
2163 if (d > 0)
2164 {
2165 GEN u = pol0_F2x(T[1]);
2166 long i,j;
2167 for (i=2,j=2; i<d+2; i++,j+=2)
2168 {
2169 gel(z, j) = F2xq_sqr(gel(x, i), T);
2170 gel(z, j+1) = u;
2171 }
2172 }
2173 gel(z, 2+2*d) = F2xq_sqr(gel(x, 2+d), T);
2174 return FlxX_renormalize(z, l);
2175 }
2176
2177 static GEN
F2xqX_divrem_basecase(GEN x,GEN y,GEN T,GEN * pr)2178 F2xqX_divrem_basecase(GEN x, GEN y, GEN T, GEN *pr)
2179 {
2180 long vx, dx, dy, dz, i, j, sx, lr;
2181 pari_sp av0, av, tetpil;
2182 GEN z,p1,rem,lead;
2183
2184 if (!signe(y)) pari_err_INV("F2xqX_divrem",y);
2185 vx=varn(x); dy=degpol(y); dx=degpol(x);
2186 if (dx < dy)
2187 {
2188 if (pr)
2189 {
2190 av0 = avma; x = F2xqX_red(x, T);
2191 if (pr == ONLY_DIVIDES) { set_avma(av0); return signe(x)? NULL: pol_0(vx); }
2192 if (pr == ONLY_REM) return x;
2193 *pr = x;
2194 }
2195 return pol_0(vx);
2196 }
2197 lead = leading_coeff(y);
2198 if (!dy) /* y is constant */
2199 {
2200 if (pr && pr != ONLY_DIVIDES)
2201 {
2202 if (pr == ONLY_REM) return pol_0(vx);
2203 *pr = pol_0(vx);
2204 }
2205 if (F2x_equal1(lead)) return gcopy(x);
2206 av0 = avma; x = F2xqX_F2xq_mul(x,F2xq_inv(lead,T),T);
2207 return gerepileupto(av0,x);
2208 }
2209 av0 = avma; dz = dx-dy;
2210 lead = F2x_equal1(lead)? NULL: gclone(F2xq_inv(lead,T));
2211 set_avma(av0);
2212 z = cgetg(dz+3,t_POL); z[1] = x[1];
2213 x += 2; y += 2; z += 2;
2214
2215 p1 = gel(x,dx); av = avma;
2216 gel(z,dz) = lead? gerepileupto(av, F2xq_mul(p1,lead, T)): leafcopy(p1);
2217 for (i=dx-1; i>=dy; i--)
2218 {
2219 av=avma; p1=gel(x,i);
2220 for (j=i-dy+1; j<=i && j<=dz; j++)
2221 p1 = F2x_add(p1, F2x_mul(gel(z,j),gel(y,i-j)));
2222 if (lead) p1 = F2x_mul(p1, lead);
2223 tetpil=avma; gel(z,i-dy) = gerepile(av,tetpil,F2x_rem(p1,T));
2224 }
2225 if (!pr) { guncloneNULL(lead); return z-2; }
2226
2227 rem = (GEN)avma; av = (pari_sp)new_chunk(dx+3);
2228 for (sx=0; ; i--)
2229 {
2230 p1 = gel(x,i);
2231 for (j=0; j<=i && j<=dz; j++)
2232 p1 = F2x_add(p1, F2x_mul(gel(z,j),gel(y,i-j)));
2233 tetpil=avma; p1 = F2x_rem(p1, T); if (lgpol(p1)) { sx = 1; break; }
2234 if (!i) break;
2235 set_avma(av);
2236 }
2237 if (pr == ONLY_DIVIDES)
2238 {
2239 guncloneNULL(lead);
2240 if (sx) return gc_NULL(av0);
2241 return gc_const((pari_sp)rem, z-2);
2242 }
2243 lr=i+3; rem -= lr;
2244 rem[0] = evaltyp(t_POL) | evallg(lr);
2245 rem[1] = z[-1];
2246 p1 = gerepile((pari_sp)rem,tetpil,p1);
2247 rem += 2; gel(rem,i) = p1;
2248 for (i--; i>=0; i--)
2249 {
2250 av=avma; p1 = gel(x,i);
2251 for (j=0; j<=i && j<=dz; j++)
2252 p1 = F2x_add(p1, F2x_mul(gel(z,j),gel(y,i-j)));
2253 tetpil=avma; gel(rem,i) = gerepile(av,tetpil, F2x_rem(p1, T));
2254 }
2255 rem -= 2;
2256 guncloneNULL(lead);
2257 if (!sx) (void)F2xX_renormalize(rem, lr);
2258 if (pr == ONLY_REM) return gerepileupto(av0,rem);
2259 *pr = rem; return z-2;
2260 }
2261
2262 static GEN
F2xX_recipspec(GEN x,long l,long n,long vs)2263 F2xX_recipspec(GEN x, long l, long n, long vs)
2264 {
2265 long i;
2266 GEN z = cgetg(n+2,t_POL);
2267 z[1] = 0; z += 2;
2268 for(i=0; i<l; i++)
2269 gel(z,n-i-1) = F2x_copy(gel(x,i));
2270 for( ; i<n; i++)
2271 gel(z,n-i-1) = pol0_F2x(vs);
2272 return F2xX_renormalize(z-2,n+2);
2273 }
2274
2275 static GEN
F2xqX_invBarrett_basecase(GEN T,GEN Q)2276 F2xqX_invBarrett_basecase(GEN T, GEN Q)
2277 {
2278 long i, l=lg(T)-1, lr = l-1, k;
2279 long sv=Q[1];
2280 GEN r=cgetg(lr,t_POL); r[1]=T[1];
2281 gel(r,2) = pol1_F2x(sv);
2282 for (i=3;i<lr;i++)
2283 {
2284 pari_sp ltop=avma;
2285 GEN u = gel(T,l-i+2);
2286 for (k=3;k<i;k++)
2287 u = F2x_add(u, F2xq_mul(gel(T,l-i+k),gel(r,k),Q));
2288 gel(r,i) = gerepileupto(ltop, u);
2289 }
2290 r = F2xX_renormalize(r,lr);
2291 return r;
2292 }
2293
2294 /* Return new lgpol */
2295 static long
F2xX_lgrenormalizespec(GEN x,long lx)2296 F2xX_lgrenormalizespec(GEN x, long lx)
2297 {
2298 long i;
2299 for (i = lx-1; i>=0; i--)
2300 if (lgpol(gel(x,i))) break;
2301 return i+1;
2302 }
2303
2304 static GEN
F2xqX_invBarrett_Newton(GEN S,GEN T)2305 F2xqX_invBarrett_Newton(GEN S, GEN T)
2306 {
2307 pari_sp av = avma;
2308 long nold, lx, lz, lq, l = degpol(S), i, lQ;
2309 GEN q, y, z, x = cgetg(l+2, t_POL) + 2;
2310 long dT = get_F2x_degree(T);
2311 ulong mask = quadratic_prec_mask(l-2); /* assume l > 2 */
2312 for (i=0;i<l;i++) gel(x,i) = pol0_F2x(T[1]);
2313 q = F2xX_recipspec(S+2,l+1,l+1,dT);
2314 lQ = lgpol(q); q+=2;
2315 /* We work on _spec_ FlxX's, all the l[xzq] below are lgpol's */
2316
2317 /* initialize */
2318 gel(x,0) = F2xq_inv(gel(q,0),T);
2319 if (lQ>1 && F2x_degree(gel(q,1)) >= dT)
2320 gel(q,1) = F2x_rem(gel(q,1), T);
2321 if (lQ>1 && lgpol(gel(q,1)))
2322 {
2323 GEN u = gel(q, 1);
2324 if (!F2x_equal1(gel(x,0))) u = F2xq_mul(u, F2xq_sqr(gel(x,0), T), T);
2325 else u = F2x_copy(u);
2326 gel(x,1) = u; lx = 2;
2327 }
2328 else
2329 lx = 1;
2330 nold = 1;
2331 for (; mask > 1; )
2332 { /* set x -= x(x*q - 1) + O(t^(nnew + 1)), knowing x*q = 1 + O(t^(nold+1)) */
2333 long i, lnew, nnew = nold << 1;
2334
2335 if (mask & 1) nnew--;
2336 mask >>= 1;
2337
2338 lnew = nnew + 1;
2339 lq = F2xX_lgrenormalizespec(q, minss(lQ,lnew));
2340 z = F2xqX_mulspec(x, q, T, lx, lq); /* FIXME: high product */
2341 lz = lgpol(z); if (lz > lnew) lz = lnew;
2342 z += 2;
2343 /* subtract 1 [=>first nold words are 0]: renormalize so that z(0) != 0 */
2344 for (i = nold; i < lz; i++) if (lgpol(gel(z,i))) break;
2345 nold = nnew;
2346 if (i >= lz) continue; /* z-1 = 0(t^(nnew + 1)) */
2347
2348 /* z + i represents (x*q - 1) / t^i */
2349 lz = F2xX_lgrenormalizespec (z+i, lz-i);
2350 z = F2xqX_mulspec(x, z+i, T, lx, lz); /* FIXME: low product */
2351 lz = lgpol(z); z += 2;
2352 if (lz > lnew-i) lz = F2xX_lgrenormalizespec(z, lnew-i);
2353
2354 lx = lz+ i;
2355 y = x + i; /* x -= z * t^i, in place */
2356 for (i = 0; i < lz; i++) gel(y,i) = gel(z,i);
2357 }
2358 x -= 2; setlg(x, lx + 2); x[1] = S[1];
2359 return gerepilecopy(av, x);
2360 }
2361
2362 GEN
F2xqX_invBarrett(GEN T,GEN Q)2363 F2xqX_invBarrett(GEN T, GEN Q)
2364 {
2365 pari_sp ltop=avma;
2366 long l=lg(T), v = varn(T);
2367 GEN r;
2368 GEN c = gel(T,l-1);
2369 if (l<5) return pol_0(v);
2370 if (l<=F2xqX_INVBARRETT_LIMIT)
2371 {
2372 if (!F2x_equal1(c))
2373 {
2374 GEN ci = F2xq_inv(c,Q);
2375 T = F2xqX_F2xq_mul(T, ci, Q);
2376 r = F2xqX_invBarrett_basecase(T,Q);
2377 r = F2xqX_F2xq_mul(r,ci,Q);
2378 } else
2379 r = F2xqX_invBarrett_basecase(T,Q);
2380 } else
2381 r = F2xqX_invBarrett_Newton(T,Q);
2382 return gerepileupto(ltop, r);
2383 }
2384
2385 GEN
F2xqX_get_red(GEN S,GEN T)2386 F2xqX_get_red(GEN S, GEN T)
2387 {
2388 if (typ(S)==t_POL && lg(S)>F2xqX_BARRETT_LIMIT)
2389 retmkvec2(F2xqX_invBarrett(S, T), S);
2390 return S;
2391 }
2392
2393 /* Compute x mod S where 2 <= degpol(S) <= l+1 <= 2*(degpol(S)-1)
2394 * * and mg is the Barrett inverse of S. */
2395 static GEN
F2xqX_divrem_Barrettspec(GEN x,long l,GEN mg,GEN S,GEN T,GEN * pr)2396 F2xqX_divrem_Barrettspec(GEN x, long l, GEN mg, GEN S, GEN T, GEN *pr)
2397 {
2398 GEN q, r;
2399 long lt = degpol(S); /*We discard the leading term*/
2400 long ld, lm, lT, lmg;
2401 ld = l-lt;
2402 lm = minss(ld, lgpol(mg));
2403 lT = F2xX_lgrenormalizespec(S+2,lt);
2404 lmg = F2xX_lgrenormalizespec(mg+2,lm);
2405 q = F2xX_recipspec(x+lt,ld,ld,0); /* q = rec(x) lq<=ld*/
2406 q = F2xqX_mulspec(q+2,mg+2,T,lgpol(q),lmg); /* q = rec(x) * mg lq<=ld+lm*/
2407 q = F2xX_recipspec(q+2,minss(ld,lgpol(q)),ld,0);/* q = rec (rec(x) * mg) lq<=ld*/
2408 if (!pr) return q;
2409 r = F2xqX_mulspec(q+2,S+2,T,lgpol(q),lT); /* r = q*pol lr<=ld+lt*/
2410 r = F2xX_addspec(x,r+2,lt,minss(lt,lgpol(r)));/* r = x - r lr<=lt */
2411 if (pr == ONLY_REM) return r;
2412 *pr = r; return q;
2413 }
2414
2415 static GEN
F2xqX_divrem_Barrett(GEN x,GEN mg,GEN S,GEN T,GEN * pr)2416 F2xqX_divrem_Barrett(GEN x, GEN mg, GEN S, GEN T, GEN *pr)
2417 {
2418 GEN q = NULL, r = F2xqX_red(x, T);
2419 long l = lgpol(r), lt = degpol(S), lm = 2*lt-1, v = varn(S);
2420 long i;
2421 if (l <= lt)
2422 {
2423 if (pr == ONLY_REM) return r;
2424 if (pr == ONLY_DIVIDES) return signe(r)? NULL: pol_0(v);
2425 if (pr) *pr = r;
2426 return pol_0(v);
2427 }
2428 if (lt <= 1)
2429 return F2xqX_divrem_basecase(x,S,T,pr);
2430 if (pr != ONLY_REM && l>lm)
2431 {
2432 long vT = get_F2x_var(T);
2433 q = cgetg(l-lt+2, t_POL); q[1] = S[1];
2434 for (i=0;i<l-lt;i++) gel(q+2,i) = pol0_F2x(vT);
2435 }
2436 while (l>lm)
2437 {
2438 GEN zr, zq = F2xqX_divrem_Barrettspec(r+2+l-lm,lm,mg,S,T,&zr);
2439 long lz = lgpol(zr);
2440 if (pr != ONLY_REM)
2441 {
2442 long lq = lgpol(zq);
2443 for(i=0; i<lq; i++) gel(q+2+l-lm,i) = gel(zq,2+i);
2444 }
2445 for(i=0; i<lz; i++) gel(r+2+l-lm,i) = gel(zr,2+i);
2446 l = l-lm+lz;
2447 }
2448 if (pr == ONLY_REM)
2449 {
2450 if (l > lt)
2451 r = F2xqX_divrem_Barrettspec(r+2,l,mg,S,T,ONLY_REM);
2452 else
2453 r = F2xX_renormalize(r, lg(r));
2454 setvarn(r, v); return F2xX_renormalize(r, lg(r));
2455 }
2456 if (l > lt)
2457 {
2458 GEN zq = F2xqX_divrem_Barrettspec(r+2,l,mg,S,T,pr? &r: NULL);
2459 if (!q) q = zq;
2460 else
2461 {
2462 long lq = lgpol(zq);
2463 for(i=0; i<lq; i++) gel(q+2,i) = gel(zq,2+i);
2464 }
2465 }
2466 else if (pr)
2467 r = F2xX_renormalize(r, l+2);
2468 setvarn(q, v); q = F2xX_renormalize(q, lg(q));
2469 if (pr == ONLY_DIVIDES) return signe(r)? NULL: q;
2470 if (pr) { setvarn(r, v); *pr = r; }
2471 return q;
2472 }
2473
2474 GEN
F2xqX_divrem(GEN x,GEN S,GEN T,GEN * pr)2475 F2xqX_divrem(GEN x, GEN S, GEN T, GEN *pr)
2476 {
2477 GEN B, y;
2478 long dy, dx, d;
2479 if (pr==ONLY_REM) return F2xqX_rem(x, S, T);
2480 y = get_F2xqX_red(S, &B);
2481 dy = degpol(y); dx = degpol(x); d = dx-dy;
2482 if (!B && d+3 < F2xqX_DIVREM_BARRETT_LIMIT)
2483 return F2xqX_divrem_basecase(x,y,T,pr);
2484 else
2485 {
2486 pari_sp av=avma;
2487 GEN mg = B? B: F2xqX_invBarrett(y, T);
2488 GEN q = F2xqX_divrem_Barrett(x,mg,y,T,pr);
2489 if (!q) return gc_NULL(av);
2490 if (!pr || pr==ONLY_DIVIDES) return gerepilecopy(av, q);
2491 gerepileall(av,2,&q,pr);
2492 return q;
2493 }
2494 }
2495
2496 GEN
F2xqX_rem(GEN x,GEN S,GEN T)2497 F2xqX_rem(GEN x, GEN S, GEN T)
2498 {
2499 GEN B, y = get_F2xqX_red(S, &B);
2500 long dy = degpol(y), dx = degpol(x), d = dx-dy;
2501 if (d < 0) return F2xqX_red(x, T);
2502 if (!B && d+3 < F2xqX_REM_BARRETT_LIMIT)
2503 return F2xqX_divrem_basecase(x,y, T, ONLY_REM);
2504 else
2505 {
2506 pari_sp av=avma;
2507 GEN mg = B? B: F2xqX_invBarrett(y, T);
2508 GEN r = F2xqX_divrem_Barrett(x, mg, y, T, ONLY_REM);
2509 return gerepileupto(av, r);
2510 }
2511 }
2512
2513 static GEN
F2xqX_halfgcd_basecase(GEN a,GEN b,GEN T)2514 F2xqX_halfgcd_basecase(GEN a, GEN b, GEN T)
2515 {
2516 pari_sp av=avma;
2517 GEN u,u1,v,v1;
2518 long vx = varn(a);
2519 long n = lgpol(a)>>1;
2520 u1 = v = pol_0(vx);
2521 u = v1 = pol1_F2xX(vx, get_F2x_var(T));
2522 while (lgpol(b)>n)
2523 {
2524 GEN r, q = F2xqX_divrem(a,b, T, &r);
2525 a = b; b = r; swap(u,u1); swap(v,v1);
2526 u1 = F2xX_add(u1, F2xqX_mul(u, q, T));
2527 v1 = F2xX_add(v1, F2xqX_mul(v, q ,T));
2528 if (gc_needed(av,2))
2529 {
2530 if (DEBUGMEM>1) pari_warn(warnmem,"F2xqX_halfgcd (d = %ld)",degpol(b));
2531 gerepileall(av,6, &a,&b,&u1,&v1,&u,&v);
2532 }
2533 }
2534 return gerepilecopy(av, mkmat2(mkcol2(u,u1), mkcol2(v,v1)));
2535 }
2536 static GEN
F2xqX_addmulmul(GEN u,GEN v,GEN x,GEN y,GEN T)2537 F2xqX_addmulmul(GEN u, GEN v, GEN x, GEN y, GEN T)
2538 {
2539 return F2xX_add(F2xqX_mul(u, x, T),F2xqX_mul(v, y, T));
2540 }
2541
2542 static GEN
F2xqXM_F2xqX_mul2(GEN M,GEN x,GEN y,GEN T)2543 F2xqXM_F2xqX_mul2(GEN M, GEN x, GEN y, GEN T)
2544 {
2545 GEN res = cgetg(3, t_COL);
2546 gel(res, 1) = F2xqX_addmulmul(gcoeff(M,1,1), gcoeff(M,1,2), x, y, T);
2547 gel(res, 2) = F2xqX_addmulmul(gcoeff(M,2,1), gcoeff(M,2,2), x, y, T);
2548 return res;
2549 }
2550
2551 static GEN
F2xqXM_mul2(GEN A,GEN B,GEN T)2552 F2xqXM_mul2(GEN A, GEN B, GEN T)
2553 {
2554 GEN A11=gcoeff(A,1,1),A12=gcoeff(A,1,2), B11=gcoeff(B,1,1),B12=gcoeff(B,1,2);
2555 GEN A21=gcoeff(A,2,1),A22=gcoeff(A,2,2), B21=gcoeff(B,2,1),B22=gcoeff(B,2,2);
2556 GEN M1 = F2xqX_mul(F2xX_add(A11,A22), F2xX_add(B11,B22), T);
2557 GEN M2 = F2xqX_mul(F2xX_add(A21,A22), B11, T);
2558 GEN M3 = F2xqX_mul(A11, F2xX_add(B12,B22), T);
2559 GEN M4 = F2xqX_mul(A22, F2xX_add(B21,B11), T);
2560 GEN M5 = F2xqX_mul(F2xX_add(A11,A12), B22, T);
2561 GEN M6 = F2xqX_mul(F2xX_add(A21,A11), F2xX_add(B11,B12), T);
2562 GEN M7 = F2xqX_mul(F2xX_add(A12,A22), F2xX_add(B21,B22), T);
2563 GEN T1 = F2xX_add(M1,M4), T2 = F2xX_add(M7,M5);
2564 GEN T3 = F2xX_add(M1,M2), T4 = F2xX_add(M3,M6);
2565 retmkmat2(mkcol2(F2xX_add(T1,T2), F2xX_add(M2,M4)),
2566 mkcol2(F2xX_add(M3,M5), F2xX_add(T3,T4)));
2567 }
2568
2569 /* Return [0,1;1,-q]*M */
2570 static GEN
F2xqX_F2xqXM_qmul(GEN q,GEN M,GEN T)2571 F2xqX_F2xqXM_qmul(GEN q, GEN M, GEN T)
2572 {
2573 GEN u, v, res = cgetg(3, t_MAT);
2574 u = F2xX_add(gcoeff(M,1,1), F2xqX_mul(gcoeff(M,2,1), q, T));
2575 gel(res,1) = mkcol2(gcoeff(M,2,1), u);
2576 v = F2xX_add(gcoeff(M,1,2), F2xqX_mul(gcoeff(M,2,2), q, T));
2577 gel(res,2) = mkcol2(gcoeff(M,2,2), v);
2578 return res;
2579 }
2580
2581 static GEN
matid2_F2xXM(long v,long sv)2582 matid2_F2xXM(long v, long sv)
2583 {
2584 retmkmat2(mkcol2(pol1_F2xX(v, sv),pol_0(v)),
2585 mkcol2(pol_0(v),pol1_F2xX(v, sv)));
2586 }
2587
2588 static GEN
F2xqX_halfgcd_split(GEN x,GEN y,GEN T)2589 F2xqX_halfgcd_split(GEN x, GEN y, GEN T)
2590 {
2591 pari_sp av=avma;
2592 GEN R, S, V;
2593 GEN y1, r, q;
2594 long l = lgpol(x), n = l>>1, k;
2595 if (lgpol(y)<=n) return matid2_F2xXM(varn(x),get_F2x_var(T));
2596 R = F2xqX_halfgcd(RgX_shift_shallow(x,-n),RgX_shift_shallow(y,-n), T);
2597 V = F2xqXM_F2xqX_mul2(R,x,y, T); y1 = gel(V,2);
2598 if (lgpol(y1)<=n) return gerepilecopy(av, R);
2599 q = F2xqX_divrem(gel(V,1), y1, T, &r);
2600 k = 2*n-degpol(y1);
2601 S = F2xqX_halfgcd(RgX_shift_shallow(y1,-k), RgX_shift_shallow(r,-k), T);
2602 return gerepileupto(av, F2xqXM_mul2(S,F2xqX_F2xqXM_qmul(q,R, T), T));
2603 }
2604
2605 /* Return M in GL_2(Fp[X]) such that:
2606 if [a',b']~=M*[a,b]~ then degpol(a')>= (lgpol(a)>>1) >degpol(b')
2607 */
2608
2609 static GEN
F2xqX_halfgcd_i(GEN x,GEN y,GEN T)2610 F2xqX_halfgcd_i(GEN x, GEN y, GEN T)
2611 {
2612 if (lg(x)<=F2xqX_HALFGCD_LIMIT) return F2xqX_halfgcd_basecase(x, y, T);
2613 return F2xqX_halfgcd_split(x, y, T);
2614 }
2615
2616 GEN
F2xqX_halfgcd(GEN x,GEN y,GEN T)2617 F2xqX_halfgcd(GEN x, GEN y, GEN T)
2618 {
2619 pari_sp av = avma;
2620 GEN M,q,r;
2621 if (!signe(x))
2622 {
2623 long v = varn(x), vT = get_F2x_var(T);
2624 retmkmat2(mkcol2(pol_0(v),pol1_F2xX(v,vT)),
2625 mkcol2(pol1_F2xX(v,vT),pol_0(v)));
2626 }
2627 if (degpol(y)<degpol(x)) return F2xqX_halfgcd_i(x, y, T);
2628 q = F2xqX_divrem(y, x, T, &r);
2629 M = F2xqX_halfgcd_i(x, r, T);
2630 gcoeff(M,1,1) = F2xX_add(gcoeff(M,1,1), F2xqX_mul(q, gcoeff(M,1,2), T));
2631 gcoeff(M,2,1) = F2xX_add(gcoeff(M,2,1), F2xqX_mul(q, gcoeff(M,2,2), T));
2632 return gerepilecopy(av, M);
2633 }
2634
2635 static GEN
F2xqX_gcd_basecase(GEN a,GEN b,GEN T)2636 F2xqX_gcd_basecase(GEN a, GEN b, GEN T)
2637 {
2638 pari_sp av = avma, av0=avma;
2639 while (signe(b))
2640 {
2641 GEN c;
2642 if (gc_needed(av0,2))
2643 {
2644 if (DEBUGMEM>1) pari_warn(warnmem,"F2xqX_gcd (d = %ld)",degpol(b));
2645 gerepileall(av0,2, &a,&b);
2646 }
2647 av = avma; c = F2xqX_rem(a, b, T); a=b; b=c;
2648 }
2649 return gc_const(av, a);
2650 }
2651
2652 GEN
F2xqX_gcd(GEN x,GEN y,GEN T)2653 F2xqX_gcd(GEN x, GEN y, GEN T)
2654 {
2655 pari_sp av = avma;
2656 x = F2xqX_red(x, T);
2657 y = F2xqX_red(y, T);
2658 if (!signe(x)) return gerepileupto(av, y);
2659 while (lg(y)>F2xqX_GCD_LIMIT)
2660 {
2661 GEN c;
2662 if (lgpol(y)<=(lgpol(x)>>1))
2663 {
2664 GEN r = F2xqX_rem(x, y, T);
2665 x = y; y = r;
2666 }
2667 c = F2xqXM_F2xqX_mul2(F2xqX_halfgcd(x,y, T), x, y, T);
2668 x = gel(c,1); y = gel(c,2);
2669 gerepileall(av,2,&x,&y);
2670 }
2671 return gerepileupto(av, F2xqX_gcd_basecase(x, y, T));
2672 }
2673
2674 static GEN
F2xqX_extgcd_basecase(GEN a,GEN b,GEN T,GEN * ptu,GEN * ptv)2675 F2xqX_extgcd_basecase(GEN a, GEN b, GEN T, GEN *ptu, GEN *ptv)
2676 {
2677 pari_sp av=avma;
2678 GEN u,v,d,d1,v1;
2679 long vx = varn(a);
2680 d = a; d1 = b;
2681 v = pol_0(vx); v1 = pol1_F2xX(vx, get_F2x_var(T));
2682 while (signe(d1))
2683 {
2684 GEN r, q = F2xqX_divrem(d, d1, T, &r);
2685 v = F2xX_add(v,F2xqX_mul(q,v1,T));
2686 u=v; v=v1; v1=u;
2687 u=r; d=d1; d1=u;
2688 if (gc_needed(av,2))
2689 {
2690 if (DEBUGMEM>1) pari_warn(warnmem,"F2xqX_extgcd (d = %ld)",degpol(d));
2691 gerepileall(av,5, &d,&d1,&u,&v,&v1);
2692 }
2693 }
2694 if (ptu) *ptu = F2xqX_div(F2xX_add(d,F2xqX_mul(b,v, T)), a, T);
2695 *ptv = v; return d;
2696 }
2697
2698 static GEN
F2xqX_extgcd_halfgcd(GEN x,GEN y,GEN T,GEN * ptu,GEN * ptv)2699 F2xqX_extgcd_halfgcd(GEN x, GEN y, GEN T, GEN *ptu, GEN *ptv)
2700 {
2701 pari_sp av=avma;
2702 GEN u,v,R = matid2_F2xXM(varn(x), get_F2x_var(T));
2703 while (lg(y)>F2xqX_EXTGCD_LIMIT)
2704 {
2705 GEN M, c;
2706 if (lgpol(y)<=(lgpol(x)>>1))
2707 {
2708 GEN r, q = F2xqX_divrem(x, y, T, &r);
2709 x = y; y = r;
2710 R = F2xqX_F2xqXM_qmul(q, R, T);
2711 }
2712 M = F2xqX_halfgcd(x,y, T);
2713 c = F2xqXM_F2xqX_mul2(M, x,y, T);
2714 R = F2xqXM_mul2(M, R, T);
2715 x = gel(c,1); y = gel(c,2);
2716 gerepileall(av,3,&x,&y,&R);
2717 }
2718 y = F2xqX_extgcd_basecase(x,y, T, &u,&v);
2719 if (ptu) *ptu = F2xqX_addmulmul(u,v,gcoeff(R,1,1),gcoeff(R,2,1), T);
2720 *ptv = F2xqX_addmulmul(u,v,gcoeff(R,1,2),gcoeff(R,2,2), T);
2721 return y;
2722 }
2723
2724 /* x and y in Z[Y][X], return lift(gcd(x mod T,p, y mod T,p)). Set u and v st
2725 * ux + vy = gcd (mod T,p) */
2726 GEN
F2xqX_extgcd(GEN x,GEN y,GEN T,GEN * ptu,GEN * ptv)2727 F2xqX_extgcd(GEN x, GEN y, GEN T, GEN *ptu, GEN *ptv)
2728 {
2729 GEN d;
2730 pari_sp ltop=avma;
2731 x = F2xqX_red(x, T);
2732 y = F2xqX_red(y, T);
2733 if (lg(y)>F2xqX_EXTGCD_LIMIT)
2734 d = F2xqX_extgcd_halfgcd(x, y, T, ptu, ptv);
2735 else
2736 d = F2xqX_extgcd_basecase(x, y, T, ptu, ptv);
2737 gerepileall(ltop,ptu?3:2,&d,ptv,ptu);
2738 return d;
2739 }
2740
2741 static GEN
_F2xqX_mul(void * data,GEN a,GEN b)2742 _F2xqX_mul(void *data,GEN a,GEN b) { return F2xqX_mul(a,b, (GEN) data); }
2743 static GEN
_F2xqX_sqr(void * data,GEN a)2744 _F2xqX_sqr(void *data,GEN a) { return F2xqX_sqr(a, (GEN) data); }
2745 GEN
F2xqX_powu(GEN x,ulong n,GEN T)2746 F2xqX_powu(GEN x, ulong n, GEN T)
2747 { return gen_powu(x, n, (void*)T, &_F2xqX_sqr, &_F2xqX_mul); }
2748
2749 /* Res(A,B) = Res(B,R) * lc(B)^(a-r) * (-1)^(ab), with R=A%B, a=deg(A) ...*/
2750 GEN
F2xqX_resultant(GEN a,GEN b,GEN T)2751 F2xqX_resultant(GEN a, GEN b, GEN T)
2752 {
2753 long vT = get_F2x_var(T);
2754 long da,db,dc;
2755 pari_sp av;
2756 GEN c,lb, res = pol1_F2x(vT);
2757
2758 if (!signe(a) || !signe(b)) return pol0_F2x(vT);
2759
2760 da = degpol(a);
2761 db = degpol(b);
2762 if (db > da)
2763 swapspec(a,b, da,db);
2764 if (!da) return pol1_F2x(vT); /* = res * a[2] ^ db, since 0 <= db <= da = 0 */
2765 av = avma;
2766 while (db)
2767 {
2768 lb = gel(b,db+2);
2769 c = F2xqX_rem(a,b, T);
2770 a = b; b = c; dc = degpol(c);
2771 if (dc < 0) { set_avma(av); return pol0_F2x(vT); }
2772
2773 if (!equali1(lb)) res = F2xq_mul(res, F2xq_powu(lb, da - dc, T), T);
2774 if (gc_needed(av,2))
2775 {
2776 if (DEBUGMEM>1) pari_warn(warnmem,"F2xqX_resultant (da = %ld)",da);
2777 gerepileall(av,3, &a,&b,&res);
2778 }
2779 da = db; /* = degpol(a) */
2780 db = dc; /* = degpol(b) */
2781 }
2782 res = F2xq_mul(res, F2xq_powu(gel(b,2), da, T), T);
2783 return gerepileupto(av, res);
2784 }
2785
2786 /* disc P = (-1)^(n(n-1)/2) lc(P)^(n - deg P' - 2) Res(P,P'), n = deg P */
2787 GEN
F2xqX_disc(GEN P,GEN T)2788 F2xqX_disc(GEN P, GEN T)
2789 {
2790 pari_sp av = avma;
2791 GEN L, dP = F2xX_deriv(P), D = F2xqX_resultant(P, dP, T);
2792 long dd;
2793 if (!lgpol(D)) return pol_0(get_F2x_var(T));
2794 dd = degpol(P) - 2 - degpol(dP); /* >= -1; > -1 iff p | deg(P) */
2795 L = leading_coeff(P);
2796 if (dd && !F2x_equal1(L))
2797 D = (dd == -1)? F2xq_div(D,L,T): F2xq_mul(D, F2xq_powu(L, dd, T), T);
2798 return gerepileupto(av, D);
2799 }
2800
2801 /***********************************************************************/
2802 /** **/
2803 /** F2xqXQ **/
2804 /** **/
2805 /***********************************************************************/
2806
2807 GEN
F2xqXQ_mul(GEN x,GEN y,GEN S,GEN T)2808 F2xqXQ_mul(GEN x, GEN y, GEN S, GEN T) {
2809 return F2xqX_rem(F2xqX_mul(x,y,T),S,T);
2810 }
2811
2812 GEN
F2xqXQ_sqr(GEN x,GEN S,GEN T)2813 F2xqXQ_sqr(GEN x, GEN S, GEN T) {
2814 return F2xqX_rem(F2xqX_sqr(x,T),S,T);
2815 }
2816
2817 GEN
F2xqXQ_invsafe(GEN x,GEN S,GEN T)2818 F2xqXQ_invsafe(GEN x, GEN S, GEN T)
2819 {
2820 GEN V, z = F2xqX_extgcd(get_F2xqX_mod(S), x, T, NULL, &V);
2821 if (degpol(z)) return NULL;
2822 z = F2xq_invsafe(gel(z,2),T);
2823 if (!z) return NULL;
2824 return F2xqX_F2xq_mul(V, z, T);
2825 }
2826
2827 GEN
F2xqXQ_inv(GEN x,GEN S,GEN T)2828 F2xqXQ_inv(GEN x, GEN S, GEN T)
2829 {
2830 pari_sp av = avma;
2831 GEN U = F2xqXQ_invsafe(x, S, T);
2832 if (!U) pari_err_INV("F2xqXQ_inv",x);
2833 return gerepileupto(av, U);
2834 }
2835
2836 struct _F2xqXQ {
2837 GEN T, S;
2838 };
2839
2840 static GEN
_F2xqXQ_add(void * data,GEN x,GEN y)2841 _F2xqXQ_add(void *data, GEN x, GEN y) {
2842 (void) data;
2843 return F2xX_add(x,y);
2844 }
2845 static GEN
_F2xqXQ_cmul(void * data,GEN P,long a,GEN x)2846 _F2xqXQ_cmul(void *data, GEN P, long a, GEN x) {
2847 (void) data;
2848 return F2xX_F2x_mul(x,gel(P,a+2));
2849 }
2850 static GEN
_F2xqXQ_red(void * data,GEN x)2851 _F2xqXQ_red(void *data, GEN x) {
2852 struct _F2xqXQ *d = (struct _F2xqXQ*) data;
2853 return F2xqX_red(x, d->T);
2854 }
2855 static GEN
_F2xqXQ_mul(void * data,GEN x,GEN y)2856 _F2xqXQ_mul(void *data, GEN x, GEN y) {
2857 struct _F2xqXQ *d = (struct _F2xqXQ*) data;
2858 return F2xqXQ_mul(x,y, d->S,d->T);
2859 }
2860 static GEN
_F2xqXQ_sqr(void * data,GEN x)2861 _F2xqXQ_sqr(void *data, GEN x) {
2862 struct _F2xqXQ *d = (struct _F2xqXQ*) data;
2863 return F2xqXQ_sqr(x, d->S,d->T);
2864 }
2865 static GEN
_F2xqXQ_zero(void * data)2866 _F2xqXQ_zero(void *data) {
2867 struct _F2xqXQ *d = (struct _F2xqXQ*) data;
2868 return pol_0(get_F2xqX_var(d->S));
2869 }
2870 static GEN
_F2xqXQ_one(void * data)2871 _F2xqXQ_one(void *data) {
2872 struct _F2xqXQ *d = (struct _F2xqXQ*) data;
2873 return pol1_F2xX(get_F2xqX_var(d->S),get_F2x_var(d->T));
2874 }
2875
2876 static struct bb_algebra F2xqXQ_algebra = { _F2xqXQ_red,
2877 _F2xqXQ_add, _F2xqXQ_add, _F2xqXQ_mul,_F2xqXQ_sqr,_F2xqXQ_one,_F2xqXQ_zero };
2878
2879 GEN
F2xqXQ_pow(GEN x,GEN n,GEN S,GEN T)2880 F2xqXQ_pow(GEN x, GEN n, GEN S, GEN T)
2881 {
2882 struct _F2xqXQ D;
2883 long s = signe(n);
2884 if (!s) return pol1_F2xX(get_F2xqX_var(S), get_F2x_var(T));
2885 if (s < 0) x = F2xqXQ_inv(x,S,T);
2886 if (is_pm1(n)) return s < 0 ? x : gcopy(x);
2887 if (degpol(x) >= get_F2xqX_degree(S)) x = F2xqX_rem(x,S,T);
2888 D.T = F2x_get_red(T);
2889 D.S = F2xqX_get_red(S, T);
2890 return gen_pow(x, n, (void*)&D, &_F2xqXQ_sqr, &_F2xqXQ_mul);
2891 }
2892
2893 GEN
F2xqXQ_powers(GEN x,long l,GEN S,GEN T)2894 F2xqXQ_powers(GEN x, long l, GEN S, GEN T)
2895 {
2896 struct _F2xqXQ D;
2897 int use_sqr = 2*degpol(x) >= get_F2xqX_degree(S);
2898 D.T = F2x_get_red(T);
2899 D.S = F2xqX_get_red(S, T);
2900 return gen_powers(x, l, use_sqr, (void*)&D, &_F2xqXQ_sqr, &_F2xqXQ_mul,&_F2xqXQ_one);
2901 }
2902
2903 GEN
F2xqX_F2xqXQV_eval(GEN P,GEN V,GEN S,GEN T)2904 F2xqX_F2xqXQV_eval(GEN P, GEN V, GEN S, GEN T)
2905 {
2906 struct _F2xqXQ D;
2907 D.T = F2x_get_red(T);
2908 D.S = F2xqX_get_red(S, T);
2909 return gen_bkeval_powers(P, degpol(P), V, (void*)&D, &F2xqXQ_algebra,
2910 _F2xqXQ_cmul);
2911 }
2912
2913 GEN
F2xqX_F2xqXQ_eval(GEN Q,GEN x,GEN S,GEN T)2914 F2xqX_F2xqXQ_eval(GEN Q, GEN x, GEN S, GEN T)
2915 {
2916 struct _F2xqXQ D;
2917 int use_sqr = 2*degpol(x) >= get_F2xqX_degree(S);
2918 D.T = F2x_get_red(T);
2919 D.S = F2xqX_get_red(S, T);
2920 return gen_bkeval(Q, degpol(Q), x, use_sqr, (void*)&D, &F2xqXQ_algebra,
2921 _F2xqXQ_cmul);
2922 }
2923
2924 static GEN
F2xqXQ_autpow_sqr(void * E,GEN x)2925 F2xqXQ_autpow_sqr(void * E, GEN x)
2926 {
2927 struct _F2xqXQ *D = (struct _F2xqXQ *)E;
2928 GEN T = D->T;
2929 GEN phi = gel(x,1), S = gel(x,2);
2930 long n = brent_kung_optpow(get_F2x_degree(T)-1,lgpol(S)+1,1);
2931 GEN V = F2xq_powers(phi, n, T);
2932 GEN phi2 = F2x_F2xqV_eval(phi, V, T);
2933 GEN Sphi = F2xY_F2xqV_evalx(S, V, T);
2934 GEN S2 = F2xqX_F2xqXQ_eval(Sphi, S, D->S, T);
2935 return mkvec2(phi2, S2);
2936 }
2937
2938 static GEN
F2xqXQ_autpow_mul(void * E,GEN x,GEN y)2939 F2xqXQ_autpow_mul(void * E, GEN x, GEN y)
2940 {
2941 struct _F2xqXQ *D = (struct _F2xqXQ *)E;
2942 GEN T = D->T;
2943 GEN phi1 = gel(x,1), S1 = gel(x,2);
2944 GEN phi2 = gel(y,1), S2 = gel(y,2);
2945 long n = brent_kung_optpow(get_F2x_degree(T)-1,lgpol(S1)+1,1);
2946 GEN V = F2xq_powers(phi2, n, T);
2947 GEN phi3 = F2x_F2xqV_eval(phi1,V,T);
2948 GEN Sphi = F2xY_F2xqV_evalx(S1,V,T);
2949 GEN S3 = F2xqX_F2xqXQ_eval(Sphi, S2, D->S, T);
2950 return mkvec2(phi3, S3);
2951 }
2952
2953 GEN
F2xqXQ_autpow(GEN aut,long n,GEN S,GEN T)2954 F2xqXQ_autpow(GEN aut, long n, GEN S, GEN T)
2955 {
2956 struct _F2xqXQ D;
2957 D.T = F2x_get_red(T);
2958 D.S = F2xqX_get_red(S, T);
2959 return gen_powu(aut,n,&D,F2xqXQ_autpow_sqr,F2xqXQ_autpow_mul);
2960 }
2961
2962 static GEN
F2xqXQ_auttrace_mul(void * E,GEN x,GEN y)2963 F2xqXQ_auttrace_mul(void *E, GEN x, GEN y)
2964 {
2965 struct _F2xqXQ *D = (struct _F2xqXQ *) E;
2966 GEN T = D->T;
2967 GEN phi1 = gel(x,1), S1 = gel(x,2), a1 = gel(x,3);
2968 GEN phi2 = gel(y,1), S2 = gel(y,2), a2 = gel(y,3);
2969 long n2 = brent_kung_optpow(get_F2x_degree(T)-1, lgpol(S1)+lgpol(a1)+1, 1);
2970 GEN V2 = F2xq_powers(phi2, n2, T);
2971 GEN phi3 = F2x_F2xqV_eval(phi1, V2, T);
2972 GEN Sphi = F2xY_F2xqV_evalx(S1, V2, T);
2973 GEN aphi = F2xY_F2xqV_evalx(a1, V2, T);
2974 long n = brent_kung_optpow(maxss(degpol(Sphi),degpol(aphi)),2,1);
2975 GEN V = F2xqXQ_powers(S2, n, D->S, T);
2976 GEN S3 = F2xqX_F2xqXQV_eval(Sphi, V, D->S, T);
2977 GEN aS = F2xqX_F2xqXQV_eval(aphi, V, D->S, T);
2978 GEN a3 = F2xX_add(aS, a2);
2979 return mkvec3(phi3, S3, a3);
2980 }
2981
2982 static GEN
F2xqXQ_auttrace_sqr(void * E,GEN x)2983 F2xqXQ_auttrace_sqr(void *E, GEN x) { return F2xqXQ_auttrace_mul(E, x, x); }
2984 GEN
F2xqXQ_auttrace(GEN aut,long n,GEN S,GEN T)2985 F2xqXQ_auttrace(GEN aut, long n, GEN S, GEN T)
2986 {
2987 struct _F2xqXQ D;
2988 D.T = F2x_get_red(T);
2989 D.S = F2xqX_get_red(S, T);
2990 return gen_powu(aut,n,&D,F2xqXQ_auttrace_sqr,F2xqXQ_auttrace_mul);
2991 }
2992
2993 GEN
F2xqXQV_red(GEN x,GEN S,GEN T)2994 F2xqXQV_red(GEN x, GEN S, GEN T)
2995 { pari_APPLY_type(t_VEC, F2xqX_rem(gel(x,i), S, T)) }
2996