1 /* mpn_toom2_sqr -- Square {ap,an}. 2 3 Contributed to the GNU project by Torbjorn Granlund. 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 2006, 2007, 2008, 2009, 2010 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 /* Evaluate in: -1, 0, +inf 31 32 <-s--><--n--> 33 ____ ______ 34 |_a1_|___a0_| 35 36 v0 = a0 ^2 # A(0)^2 37 vm1 = (a0- a1)^2 # A(-1)^2 38 vinf= a1 ^2 # A(inf)^2 39 */ 40 41 #if TUNE_PROGRAM_BUILD 42 #define MAYBE_sqr_toom2 1 43 #else 44 #define MAYBE_sqr_toom2 \ 45 (SQR_TOOM3_THRESHOLD >= 2 * SQR_TOOM2_THRESHOLD) 46 #endif 47 48 #define TOOM2_SQR_REC(p, a, n, ws) \ 49 do { \ 50 if (! MAYBE_sqr_toom2 \ 51 || BELOW_THRESHOLD (n, SQR_TOOM2_THRESHOLD)) \ 52 mpn_sqr_basecase (p, a, n); \ 53 else \ 54 mpn_toom2_sqr (p, a, n, ws); \ 55 } while (0) 56 57 void 58 mpn_toom2_sqr (mp_ptr pp, 59 mp_srcptr ap, mp_size_t an, 60 mp_ptr scratch) 61 { 62 mp_size_t n, s; 63 mp_limb_t cy, cy2; 64 mp_ptr asm1; 65 66 #define a0 ap 67 #define a1 (ap + n) 68 69 s = an >> 1; 70 n = an - s; 71 72 ASSERT (0 < s && s <= n); 73 74 asm1 = pp; 75 76 /* Compute asm1. */ 77 if (s == n) 78 { 79 if (mpn_cmp (a0, a1, n) < 0) 80 { 81 mpn_sub_n (asm1, a1, a0, n); 82 } 83 else 84 { 85 mpn_sub_n (asm1, a0, a1, n); 86 } 87 } 88 else 89 { 90 if (mpn_zero_p (a0 + s, n - s) && mpn_cmp (a0, a1, s) < 0) 91 { 92 mpn_sub_n (asm1, a1, a0, s); 93 MPN_ZERO (asm1 + s, n - s); 94 } 95 else 96 { 97 mpn_sub (asm1, a0, n, a1, s); 98 } 99 } 100 101 #define v0 pp /* 2n */ 102 #define vinf (pp + 2 * n) /* s+s */ 103 #define vm1 scratch /* 2n */ 104 #define scratch_out scratch + 2 * n 105 106 /* vm1, 2n limbs */ 107 TOOM2_SQR_REC (vm1, asm1, n, scratch_out); 108 109 /* vinf, s+s limbs */ 110 TOOM2_SQR_REC (vinf, a1, s, scratch_out); 111 112 /* v0, 2n limbs */ 113 TOOM2_SQR_REC (v0, ap, n, scratch_out); 114 115 /* H(v0) + L(vinf) */ 116 cy = mpn_add_n (pp + 2 * n, v0 + n, vinf, n); 117 118 /* L(v0) + H(v0) */ 119 cy2 = cy + mpn_add_n (pp + n, pp + 2 * n, v0, n); 120 121 /* L(vinf) + H(vinf) */ 122 cy += mpn_add (pp + 2 * n, pp + 2 * n, n, vinf + n, s + s - n); 123 124 cy -= mpn_sub_n (pp + n, pp + n, vm1, 2 * n); 125 126 ASSERT (cy + 1 <= 3); 127 ASSERT (cy2 <= 2); 128 129 mpn_incr_u (pp + 2 * n, cy2); 130 if (LIKELY (cy <= 2)) 131 mpn_incr_u (pp + 3 * n, cy); 132 else 133 mpn_decr_u (pp + 3 * n, 1); 134 } 135