1 /* mpn_toom_eval_pm2rexp -- Evaluate a polynomial in +2^-k and -2^-k 2 3 Contributed to the GNU project by Marco Bodrato 4 5 THE FUNCTION IN THIS FILE IS INTERNAL WITH A MUTABLE INTERFACE. IT IS ONLY 6 SAFE TO REACH IT THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST 7 GUARANTEED THAT IT WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE. 8 9 Copyright 2009 Free Software Foundation, Inc. 10 11 This file is part of the GNU MP Library. 12 13 The GNU MP Library is free software; you can redistribute it and/or modify 14 it under the terms of the GNU Lesser General Public License as published by 15 the Free Software Foundation; either version 3 of the License, or (at your 16 option) any later version. 17 18 The GNU MP Library is distributed in the hope that it will be useful, but 19 WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 20 or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 21 License for more details. 22 23 You should have received a copy of the GNU Lesser General Public License 24 along with the GNU MP Library. If not, see http://www.gnu.org/licenses/. */ 25 26 27 #include "gmp.h" 28 #include "gmp-impl.h" 29 30 #if HAVE_NATIVE_mpn_addlsh_n 31 #define DO_mpn_addlsh_n(dst,src,n,s,ws) mpn_addlsh_n(dst,dst,src,n,s) 32 #else 33 static mp_limb_t 34 DO_mpn_addlsh_n(mp_ptr dst, mp_srcptr src, mp_size_t n, unsigned int s, mp_ptr ws) 35 { 36 #if USE_MUL_1 && 0 37 return mpn_addmul_1(dst,src,n,CNST_LIMB(1) <<(s)); 38 #else 39 mp_limb_t __cy; 40 __cy = mpn_lshift(ws,src,n,s); 41 return __cy + mpn_add_n(dst,dst,ws,n); 42 #endif 43 } 44 #endif 45 46 /* Evaluates a polynomial of degree k >= 3. */ 47 int 48 mpn_toom_eval_pm2rexp (mp_ptr rp, mp_ptr rm, 49 unsigned int q, mp_srcptr ap, mp_size_t n, mp_size_t t, 50 unsigned int s, mp_ptr ws) 51 { 52 unsigned int i; 53 int neg; 54 /* {ap,q*n+t} -> {rp,n+1} {rm,n+1} , with {ws, n+1}*/ 55 ASSERT (n >= t); 56 ASSERT (s != 0); /* or _eval_pm1 should be used */ 57 ASSERT (q > 1); 58 ASSERT (s*q < GMP_NUMB_BITS); 59 rp[n] = mpn_lshift(rp, ap, n, s*q); 60 ws[n] = mpn_lshift(ws, ap+n, n, s*(q-1)); 61 if( (q & 1) != 0) { 62 ASSERT_NOCARRY(mpn_add(ws,ws,n+1,ap+n*q,t)); 63 rp[n] += DO_mpn_addlsh_n(rp, ap+n*(q-1), n, s, rm); 64 } else { 65 ASSERT_NOCARRY(mpn_add(rp,rp,n+1,ap+n*q,t)); 66 } 67 for(i=2; i<q-1; i++) 68 { 69 rp[n] += DO_mpn_addlsh_n(rp, ap+n*i, n, s*(q-i), rm); 70 i++; 71 ws[n] += DO_mpn_addlsh_n(ws, ap+n*i, n, s*(q-i), rm); 72 }; 73 74 neg = (mpn_cmp (rp, ws, n + 1) < 0) ? ~0 : 0; 75 76 #if HAVE_NATIVE_mpn_add_n_sub_n 77 if (neg) 78 mpn_add_n_sub_n (rp, rm, ws, rp, n + 1); 79 else 80 mpn_add_n_sub_n (rp, rm, rp, ws, n + 1); 81 #else /* !HAVE_NATIVE_mpn_add_n_sub_n */ 82 if (neg) 83 mpn_sub_n (rm, ws, rp, n + 1); 84 else 85 mpn_sub_n (rm, rp, ws, n + 1); 86 87 ASSERT_NOCARRY (mpn_add_n (rp, rp, ws, n + 1)); 88 #endif /* !HAVE_NATIVE_mpn_add_n_sub_n */ 89 90 return neg; 91 } 92