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 9Copyright 2009 Free Software Foundation, Inc. 10 11This file is part of the GNU MP Library. 12 13The GNU MP Library is free software; you can redistribute it and/or modify 14it under the terms of the GNU Lesser General Public License as published by 15the Free Software Foundation; either version 3 of the License, or (at your 16option) any later version. 17 18The GNU MP Library is distributed in the hope that it will be useful, but 19WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 20or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public 21License for more details. 22 23You should have received a copy of the GNU Lesser General Public License 24along 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 33static mp_limb_t 34DO_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. */ 47int 48mpn_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