1 /* mpn_toom_eval_dgr3_pm2 -- Evaluate a degree 3 polynomial in +2 and -2 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 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 /* Needs n+1 limbs of temporary storage. */ 31 int 32 mpn_toom_eval_dgr3_pm2 (mp_ptr xp2, mp_ptr xm2, 33 mp_srcptr xp, mp_size_t n, mp_size_t x3n, mp_ptr tp) 34 { 35 mp_limb_t cy; 36 int neg; 37 38 ASSERT (x3n > 0); 39 ASSERT (x3n <= n); 40 41 /* (x0 + 4 * x2) +/- (2 x1 + 8 x_3) */ 42 #if HAVE_NATIVE_mpn_addlsh_n || HAVE_NATIVE_mpn_addlsh2_n 43 #if HAVE_NATIVE_mpn_addlsh2_n 44 xp2[n] = mpn_addlsh2_n (xp2, xp, xp + 2*n, n); 45 46 cy = mpn_addlsh2_n (tp, xp + n, xp + 3*n, x3n); 47 #else /* HAVE_NATIVE_mpn_addlsh_n */ 48 xp2[n] = mpn_addlsh_n (xp2, xp, xp + 2*n, n, 2); 49 50 cy = mpn_addlsh_n (tp, xp + n, xp + 3*n, x3n, 2); 51 #endif 52 if (x3n < n) 53 cy = mpn_add_1 (tp + x3n, xp + n + x3n, n - x3n, cy); 54 tp[n] = cy; 55 #else 56 cy = mpn_lshift (tp, xp + 2*n, n, 2); 57 xp2[n] = cy + mpn_add_n (xp2, tp, xp, n); 58 59 tp[x3n] = mpn_lshift (tp, xp + 3*n, x3n, 2); 60 if (x3n < n) 61 tp[n] = mpn_add (tp, xp + n, n, tp, x3n + 1); 62 else 63 tp[n] += mpn_add_n (tp, xp + n, tp, n); 64 #endif 65 mpn_lshift (tp, tp, n+1, 1); 66 67 neg = (mpn_cmp (xp2, tp, n + 1) < 0) ? ~0 : 0; 68 69 #if HAVE_NATIVE_mpn_add_n_sub_n 70 if (neg) 71 mpn_add_n_sub_n (xp2, xm2, tp, xp2, n + 1); 72 else 73 mpn_add_n_sub_n (xp2, xm2, xp2, tp, n + 1); 74 #else 75 if (neg) 76 mpn_sub_n (xm2, tp, xp2, n + 1); 77 else 78 mpn_sub_n (xm2, xp2, tp, n + 1); 79 80 mpn_add_n (xp2, xp2, tp, n + 1); 81 #endif 82 83 ASSERT (xp2[n] < 15); 84 ASSERT (xm2[n] < 10); 85 86 return neg; 87 } 88