1/* mpn_toom_eval_pm2exp -- Evaluate a polynomial in +2^k and -2^k 2 3 Contributed to the GNU project by Niels M��ller 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 either: 15 16 * the GNU Lesser General Public License as published by the Free 17 Software Foundation; either version 3 of the License, or (at your 18 option) any later version. 19 20or 21 22 * the GNU General Public License as published by the Free Software 23 Foundation; either version 2 of the License, or (at your option) any 24 later version. 25 26or both in parallel, as here. 27 28The GNU MP Library is distributed in the hope that it will be useful, but 29WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY 30or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 31for more details. 32 33You should have received copies of the GNU General Public License and the 34GNU Lesser General Public License along with the GNU MP Library. If not, 35see https://www.gnu.org/licenses/. */ 36 37 38#include "gmp-impl.h" 39 40/* Evaluates a polynomial of degree k > 2, in the points +2^shift and -2^shift. */ 41int 42mpn_toom_eval_pm2exp (mp_ptr xp2, mp_ptr xm2, unsigned k, 43 mp_srcptr xp, mp_size_t n, mp_size_t hn, unsigned shift, 44 mp_ptr tp) 45{ 46 unsigned i; 47 int neg; 48#if HAVE_NATIVE_mpn_addlsh_n 49 mp_limb_t cy; 50#endif 51 52 ASSERT (k >= 3); 53 ASSERT (shift*k < GMP_NUMB_BITS); 54 55 ASSERT (hn > 0); 56 ASSERT (hn <= n); 57 58 /* The degree k is also the number of full-size coefficients, so 59 * that last coefficient, of size hn, starts at xp + k*n. */ 60 61#if HAVE_NATIVE_mpn_addlsh_n 62 xp2[n] = mpn_addlsh_n (xp2, xp, xp + 2*n, n, 2*shift); 63 for (i = 4; i < k; i += 2) 64 xp2[n] += mpn_addlsh_n (xp2, xp2, xp + i*n, n, i*shift); 65 66 tp[n] = mpn_lshift (tp, xp+n, n, shift); 67 for (i = 3; i < k; i+= 2) 68 tp[n] += mpn_addlsh_n (tp, tp, xp+i*n, n, i*shift); 69 70 if (k & 1) 71 { 72 cy = mpn_addlsh_n (tp, tp, xp+k*n, hn, k*shift); 73 MPN_INCR_U (tp + hn, n+1 - hn, cy); 74 } 75 else 76 { 77 cy = mpn_addlsh_n (xp2, xp2, xp+k*n, hn, k*shift); 78 MPN_INCR_U (xp2 + hn, n+1 - hn, cy); 79 } 80 81#else /* !HAVE_NATIVE_mpn_addlsh_n */ 82 xp2[n] = mpn_lshift (tp, xp+2*n, n, 2*shift); 83 xp2[n] += mpn_add_n (xp2, xp, tp, n); 84 for (i = 4; i < k; i += 2) 85 { 86 xp2[n] += mpn_lshift (tp, xp + i*n, n, i*shift); 87 xp2[n] += mpn_add_n (xp2, xp2, tp, n); 88 } 89 90 tp[n] = mpn_lshift (tp, xp+n, n, shift); 91 for (i = 3; i < k; i+= 2) 92 { 93 tp[n] += mpn_lshift (xm2, xp + i*n, n, i*shift); 94 tp[n] += mpn_add_n (tp, tp, xm2, n); 95 } 96 97 xm2[hn] = mpn_lshift (xm2, xp + k*n, hn, k*shift); 98 if (k & 1) 99 mpn_add (tp, tp, n+1, xm2, hn+1); 100 else 101 mpn_add (xp2, xp2, n+1, xm2, hn+1); 102#endif /* !HAVE_NATIVE_mpn_addlsh_n */ 103 104 neg = (mpn_cmp (xp2, tp, n + 1) < 0) ? ~0 : 0; 105 106#if HAVE_NATIVE_mpn_add_n_sub_n 107 if (neg) 108 mpn_add_n_sub_n (xp2, xm2, tp, xp2, n + 1); 109 else 110 mpn_add_n_sub_n (xp2, xm2, xp2, tp, n + 1); 111#else /* !HAVE_NATIVE_mpn_add_n_sub_n */ 112 if (neg) 113 mpn_sub_n (xm2, tp, xp2, n + 1); 114 else 115 mpn_sub_n (xm2, xp2, tp, n + 1); 116 117 mpn_add_n (xp2, xp2, tp, n + 1); 118#endif /* !HAVE_NATIVE_mpn_add_n_sub_n */ 119 120 /* FIXME: the following asserts are useless if (k+1)*shift >= GMP_LIMB_BITS */ 121 ASSERT ((k+1)*shift >= GMP_LIMB_BITS || 122 xp2[n] < ((CNST_LIMB(1)<<((k+1)*shift))-1)/((CNST_LIMB(1)<<shift)-1)); 123 ASSERT ((k+2)*shift >= GMP_LIMB_BITS || 124 xm2[n] < ((CNST_LIMB(1)<<((k+2)*shift))-((k&1)?(CNST_LIMB(1)<<shift):1))/((CNST_LIMB(1)<<(2*shift))-1)); 125 126 return neg; 127} 128