1 /*
2 Copyright (C) 2016 William Hart
3 Copyright (C) 2020 Daniel Schultz
4
5 This file is part of FLINT.
6
7 FLINT is free software: you can redistribute it and/or modify it under
8 the terms of the GNU Lesser General Public License (LGPL) as published
9 by the Free Software Foundation; either version 2.1 of the License, or
10 (at your option) any later version. See <https://www.gnu.org/licenses/>.
11 */
12
13 #include "fmpz_mpoly.h"
14
15
_fmpz_mpoly_sub1(fmpz * Acoeffs,ulong * Aexps,const fmpz * Bcoeffs,const ulong * Bexps,slong Blen,const fmpz * Ccoeffs,const ulong * Cexps,slong Clen,ulong maskhi)16 slong _fmpz_mpoly_sub1(
17 fmpz * Acoeffs, ulong * Aexps,
18 const fmpz * Bcoeffs, const ulong * Bexps, slong Blen,
19 const fmpz * Ccoeffs, const ulong * Cexps, slong Clen,
20 ulong maskhi)
21 {
22 slong i = 0, j = 0, k = 0;
23
24 while (i < Blen && j < Clen)
25 {
26 if ((Bexps[i]^maskhi) > (Cexps[j]^maskhi))
27 {
28 Aexps[k] = Bexps[i];
29 fmpz_set(Acoeffs + k, Bcoeffs + i);
30 i++;
31 k++;
32 }
33 else if ((Bexps[i]^maskhi) == (Cexps[j]^maskhi))
34 {
35 Aexps[k] = Bexps[i];
36 fmpz_sub(Acoeffs + k, Bcoeffs + i, Ccoeffs + j);
37 k += !fmpz_is_zero(Acoeffs + k);
38 i++;
39 j++;
40 }
41 else
42 {
43 Aexps[k] = Cexps[j];
44 fmpz_neg(Acoeffs + k, Ccoeffs + j);
45 j++;
46 k++;
47 }
48 }
49
50 while (i < Blen)
51 {
52 Aexps[k] = Bexps[i];
53 fmpz_set(Acoeffs + k, Bcoeffs + i);
54 i++;
55 k++;
56 }
57
58 while (j < Clen)
59 {
60 Aexps[k] = Cexps[j];
61 fmpz_neg(Acoeffs + k, Ccoeffs + j);
62 j++;
63 k++;
64 }
65
66 return k;
67 }
68
_fmpz_mpoly_sub(fmpz * Acoeffs,ulong * Aexps,const fmpz * Bcoeffs,const ulong * Bexps,slong Blen,const fmpz * Ccoeffs,const ulong * Cexps,slong Clen,slong N,const ulong * cmpmask)69 slong _fmpz_mpoly_sub(
70 fmpz * Acoeffs, ulong * Aexps,
71 const fmpz * Bcoeffs, const ulong * Bexps, slong Blen,
72 const fmpz * Ccoeffs, const ulong * Cexps, slong Clen,
73 slong N,
74 const ulong * cmpmask)
75 {
76 slong i = 0, j = 0, k = 0;
77
78 if (N == 1)
79 {
80 return _fmpz_mpoly_sub1(Acoeffs, Aexps, Bcoeffs, Bexps, Blen,
81 Ccoeffs, Cexps, Clen, cmpmask[0]);
82 }
83
84 while (i < Blen && j < Clen)
85 {
86 int cmp = mpoly_monomial_cmp(Bexps + i*N, Cexps + j*N, N, cmpmask);
87
88 if (cmp > 0)
89 {
90 mpoly_monomial_set(Aexps + k*N, Bexps + i*N, N);
91 fmpz_set(Acoeffs + k, Bcoeffs + i);
92 i++;
93 k++;
94 }
95 else if (cmp == 0)
96 {
97 mpoly_monomial_set(Aexps + k*N, Bexps + i*N, N);
98 fmpz_sub(Acoeffs + k, Bcoeffs + i, Ccoeffs + j);
99 k += !fmpz_is_zero(Acoeffs + k);
100 i++;
101 j++;
102 }
103 else
104 {
105 mpoly_monomial_set(Aexps + k*N, Cexps + j*N, N);
106 fmpz_neg(Acoeffs + k, Ccoeffs + j);
107 j++;
108 k++;
109 }
110 }
111
112 while (i < Blen)
113 {
114 mpoly_monomial_set(Aexps + k*N, Bexps + i*N, N);
115 fmpz_set(Acoeffs + k, Bcoeffs + i);
116 i++;
117 k++;
118 }
119
120 while (j < Clen)
121 {
122 mpoly_monomial_set(Aexps + k*N, Cexps + j*N, N);
123 fmpz_neg(Acoeffs + k, Ccoeffs + j);
124 j++;
125 k++;
126 }
127
128 return k;
129 }
130
fmpz_mpoly_sub_inplace(fmpz_mpoly_t A,const fmpz_mpoly_t B,const fmpz_mpoly_ctx_t ctx)131 void fmpz_mpoly_sub_inplace(fmpz_mpoly_t A, const fmpz_mpoly_t B,
132 const fmpz_mpoly_ctx_t ctx)
133 {
134 slong i, s, new_len, N;
135 slong Alen = A->length;
136 slong Blen = B->length;
137 ulong * Bexps, * cmpmask;
138 int cmp, freeBexps;
139 flint_bitcnt_t Abits;
140 fmpz_mpoly_t T;
141 TMP_INIT;
142
143 FLINT_ASSERT(A != B);
144 FLINT_ASSERT(Alen > 0);
145 FLINT_ASSERT(Blen > 0);
146
147 TMP_START;
148
149 if (A->bits <= B->bits)
150 {
151 Abits = B->bits;
152 if (A->bits < B->bits)
153 fmpz_mpoly_repack_bits_inplace(A, Abits, ctx);
154 N = mpoly_words_per_exp(Abits, ctx->minfo);
155 Bexps = B->exps;
156 freeBexps = 0;
157 }
158 else
159 {
160 Abits = A->bits;
161 N = mpoly_words_per_exp(Abits, ctx->minfo);
162 Bexps = (ulong *) flint_malloc(N*Blen*sizeof(ulong));
163 mpoly_repack_monomials(Bexps, Abits, B->exps, B->bits, Blen, ctx->minfo);
164 freeBexps = 1;
165 }
166
167 cmpmask = (ulong *) TMP_ALLOC(N*sizeof(ulong));
168 mpoly_get_cmpmask(cmpmask, N, Abits, ctx->minfo);
169
170 for (s = 0; s < Alen/4; s++)
171 {
172 cmp = mpoly_monomial_cmp(A->exps + N*(Alen - s - 1),
173 Bexps + N*0, N, cmpmask);
174 if (cmp >= 0)
175 {
176 s += (cmp == 0);
177 goto doit;
178 }
179 }
180
181 fmpz_mpoly_init3(T, Alen + Blen, Abits, ctx);
182 T->length = _fmpz_mpoly_sub(T->coeffs, T->exps,
183 A->coeffs, A->exps, Alen,
184 B->coeffs, Bexps, Blen, N, cmpmask);
185 fmpz_mpoly_swap(A, T, ctx);
186 fmpz_mpoly_clear(T, ctx);
187 goto cleanup;
188
189 doit:
190
191 FLINT_ASSERT(0 <= s && s <= Alen);
192
193 FLINT_ASSERT(s == 0 || mpoly_monomial_cmp(A->exps + N*(Alen - s),
194 Bexps + N*0, N, cmpmask) <= 0);
195
196 FLINT_ASSERT(s == Alen || mpoly_monomial_cmp(A->exps + N*(Alen - s - 1),
197 Bexps + N*0, N, cmpmask) > 0);
198
199 fmpz_mpoly_fit_length(A, Alen + Blen + s, ctx);
200 mpoly_copy_monomials(A->exps + N*(Alen + Blen), A->exps + N*(Alen - s), s, N);
201 _fmpz_vec_swap(A->coeffs + Alen + Blen, A->coeffs + Alen - s, s);
202
203 new_len = _fmpz_mpoly_sub(A->coeffs + Alen - s, A->exps + N*(Alen - s),
204 A->coeffs + (Alen + Blen), A->exps + N*(Alen + Blen), s,
205 B->coeffs, Bexps, Blen, N, cmpmask);
206 for (i = 0; i < s; i++)
207 _fmpz_demote(A->coeffs + Alen + Blen + i);
208
209 _fmpz_mpoly_set_length(A, Alen - s + new_len, ctx);
210
211 cleanup:
212
213 if (freeBexps)
214 flint_free(Bexps);
215
216 TMP_END;
217
218 return;
219 }
220
fmpz_mpoly_sub(fmpz_mpoly_t A,const fmpz_mpoly_t B,const fmpz_mpoly_t C,const fmpz_mpoly_ctx_t ctx)221 void fmpz_mpoly_sub(fmpz_mpoly_t A, const fmpz_mpoly_t B,
222 const fmpz_mpoly_t C, const fmpz_mpoly_ctx_t ctx)
223 {
224 slong Alen, N;
225 flint_bitcnt_t Abits;
226 ulong * Bexps = B->exps, * Cexps = C->exps;
227 ulong * cmpmask;
228 int freeBexps = 0, freeCexps = 0;
229 TMP_INIT;
230
231 if (fmpz_mpoly_is_zero(B, ctx))
232 {
233 fmpz_mpoly_neg(A, C, ctx);
234 return;
235 }
236 else if (fmpz_mpoly_is_zero(C, ctx))
237 {
238 fmpz_mpoly_set(A, B, ctx);
239 return;
240 }
241 else if (A == B)
242 {
243 if (A == C)
244 fmpz_mpoly_zero(A, ctx);
245 else
246 fmpz_mpoly_sub_inplace(A, C, ctx);
247 return;
248 }
249 else if (A == C)
250 {
251 fmpz_mpoly_sub_inplace(A, B, ctx);
252 _fmpz_vec_neg(A->coeffs, A->coeffs, A->length);
253 return;
254 }
255
256 TMP_START;
257 Abits = FLINT_MAX(B->bits, C->bits);
258 N = mpoly_words_per_exp(Abits, ctx->minfo);
259 cmpmask = (ulong *) TMP_ALLOC(N*sizeof(ulong));
260 mpoly_get_cmpmask(cmpmask, N, Abits, ctx->minfo);
261
262 if (Abits > B->bits)
263 {
264 freeBexps = 1;
265 Bexps = (ulong *) flint_malloc(N*B->length*sizeof(ulong));
266 mpoly_repack_monomials(Bexps, Abits, B->exps, B->bits, B->length, ctx->minfo);
267 }
268
269 if (Abits > C->bits)
270 {
271 freeCexps = 1;
272 Cexps = (ulong *) flint_malloc(N*C->length*sizeof(ulong));
273 mpoly_repack_monomials(Cexps, Abits, C->exps, C->bits, C->length, ctx->minfo);
274 }
275
276 fmpz_mpoly_fit_length_reset_bits(A, B->length + C->length, Abits, ctx);
277
278 Alen = _fmpz_mpoly_sub(A->coeffs, A->exps,
279 B->coeffs, Bexps, B->length,
280 C->coeffs, Cexps, C->length, N, cmpmask);
281 _fmpz_mpoly_set_length(A, Alen, ctx);
282
283 if (freeBexps)
284 flint_free(Bexps);
285
286 if (freeCexps)
287 flint_free(Cexps);
288
289 TMP_END;
290 }
291