From 11da511c784eca003deb90c23570f0873954e0de Mon Sep 17 00:00:00 2001 From: Duncan Wilkie Date: Sat, 18 Nov 2023 06:11:09 -0600 Subject: Initial commit. --- gmp-6.3.0/mpn/generic/mulmod_bnm1.c | 374 ++++++++++++++++++++++++++++++++++++ 1 file changed, 374 insertions(+) create mode 100644 gmp-6.3.0/mpn/generic/mulmod_bnm1.c (limited to 'gmp-6.3.0/mpn/generic/mulmod_bnm1.c') diff --git a/gmp-6.3.0/mpn/generic/mulmod_bnm1.c b/gmp-6.3.0/mpn/generic/mulmod_bnm1.c new file mode 100644 index 0000000..8229ede --- /dev/null +++ b/gmp-6.3.0/mpn/generic/mulmod_bnm1.c @@ -0,0 +1,374 @@ +/* mulmod_bnm1.c -- multiplication mod B^n-1. + + Contributed to the GNU project by Niels Möller, Torbjorn Granlund and + Marco Bodrato. + + THE FUNCTIONS IN THIS FILE ARE INTERNAL WITH MUTABLE INTERFACES. IT IS ONLY + SAFE TO REACH THEM THROUGH DOCUMENTED INTERFACES. IN FACT, IT IS ALMOST + GUARANTEED THAT THEY WILL CHANGE OR DISAPPEAR IN A FUTURE GNU MP RELEASE. + +Copyright 2009, 2010, 2012, 2013, 2020, 2022 Free Software Foundation, Inc. + +This file is part of the GNU MP Library. + +The GNU MP Library is free software; you can redistribute it and/or modify +it under the terms of either: + + * the GNU Lesser General Public License as published by the Free + Software Foundation; either version 3 of the License, or (at your + option) any later version. + +or + + * the GNU General Public License as published by the Free Software + Foundation; either version 2 of the License, or (at your option) any + later version. + +or both in parallel, as here. + +The GNU MP Library is distributed in the hope that it will be useful, but +WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY +or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License +for more details. + +You should have received copies of the GNU General Public License and the +GNU Lesser General Public License along with the GNU MP Library. If not, +see https://www.gnu.org/licenses/. */ + + +#include "gmp-impl.h" +#include "longlong.h" + +/* Inputs are {ap,rn} and {bp,rn}; output is {rp,rn}, computation is + mod B^rn - 1, and values are semi-normalised; zero is represented + as either 0 or B^n - 1. Needs a scratch of 2rn limbs at tp. + tp==rp is allowed. */ +void +mpn_bc_mulmod_bnm1 (mp_ptr rp, mp_srcptr ap, mp_srcptr bp, mp_size_t rn, + mp_ptr tp) +{ + mp_limb_t cy; + + ASSERT (0 < rn); + + mpn_mul_n (tp, ap, bp, rn); + cy = mpn_add_n (rp, tp, tp + rn, rn); + /* If cy == 1, then the value of rp is at most B^rn - 2, so there can + * be no overflow when adding in the carry. */ + MPN_INCR_U (rp, rn, cy); +} + + +/* Inputs are {ap,rn+1} and {bp,rn+1}; output is {rp,rn+1}, in + normalised representation, computation is mod B^rn + 1. Needs + a scratch area of 2rn limbs at tp; tp == rp is allowed. + Output is normalised. */ +static void +mpn_bc_mulmod_bnp1 (mp_ptr rp, mp_srcptr ap, mp_srcptr bp, mp_size_t rn, + mp_ptr tp) +{ + mp_limb_t cy; + unsigned k; + + ASSERT (0 < rn); + + if (UNLIKELY (ap[rn] | bp [rn])) + { + if (ap[rn]) + cy = bp [rn] + mpn_neg (rp, bp, rn); + else /* ap[rn] == 0 */ + cy = mpn_neg (rp, ap, rn); + } + else if (MPN_MULMOD_BKNP1_USABLE (rn, k, MUL_FFT_MODF_THRESHOLD)) + { + mp_size_t n_k = rn / k; + TMP_DECL; + + TMP_MARK; + mpn_mulmod_bknp1 (rp, ap, bp, n_k, k, + TMP_ALLOC_LIMBS (mpn_mulmod_bknp1_itch (rn))); + TMP_FREE; + return; + } + else + { + mpn_mul_n (tp, ap, bp, rn); + cy = mpn_sub_n (rp, tp, tp + rn, rn); + } + rp[rn] = 0; + MPN_INCR_U (rp, rn + 1, cy); +} + + +/* Computes {rp,MIN(rn,an+bn)} <- {ap,an}*{bp,bn} Mod(B^rn-1) + * + * The result is expected to be ZERO if and only if one of the operand + * already is. Otherwise the class [0] Mod(B^rn-1) is represented by + * B^rn-1. This should not be a problem if mulmod_bnm1 is used to + * combine results and obtain a natural number when one knows in + * advance that the final value is less than (B^rn-1). + * Moreover it should not be a problem if mulmod_bnm1 is used to + * compute the full product with an+bn <= rn, because this condition + * implies (B^an-1)(B^bn-1) < (B^rn-1) . + * + * Requires 0 < bn <= an <= rn and an + bn > rn/2 + * Scratch need: rn + (need for recursive call OR rn + 4). This gives + * + * S(n) <= rn + MAX (rn + 4, S(n/2)) <= 2rn + 4 + */ +void +mpn_mulmod_bnm1 (mp_ptr rp, mp_size_t rn, mp_srcptr ap, mp_size_t an, mp_srcptr bp, mp_size_t bn, mp_ptr tp) +{ + ASSERT (0 < bn); + ASSERT (bn <= an); + ASSERT (an <= rn); + + if ((rn & 1) != 0 || BELOW_THRESHOLD (rn, MULMOD_BNM1_THRESHOLD)) + { + if (UNLIKELY (bn < rn)) + { + if (UNLIKELY (an + bn <= rn)) + { + mpn_mul (rp, ap, an, bp, bn); + } + else + { + mp_limb_t cy; + mpn_mul (tp, ap, an, bp, bn); + cy = mpn_add (rp, tp, rn, tp + rn, an + bn - rn); + MPN_INCR_U (rp, rn, cy); + } + } + else + mpn_bc_mulmod_bnm1 (rp, ap, bp, rn, tp); + } + else + { + mp_size_t n; + mp_limb_t cy; + mp_limb_t hi; + + n = rn >> 1; + + /* We need at least an + bn >= n, to be able to fit one of the + recursive products at rp. Requiring strict inequality makes + the code slightly simpler. If desired, we could avoid this + restriction by initially halving rn as long as rn is even and + an + bn <= rn/2. */ + + ASSERT (an + bn > n); + + /* Compute xm = a*b mod (B^n - 1), xp = a*b mod (B^n + 1) + and crt together as + + x = -xp * B^n + (B^n + 1) * [ (xp + xm)/2 mod (B^n-1)] + */ + +#define a0 ap +#define a1 (ap + n) +#define b0 bp +#define b1 (bp + n) + +#define xp tp /* 2n + 2 */ + /* am1 maybe in {xp, n} */ + /* bm1 maybe in {xp + n, n} */ +#define sp1 (tp + 2*n + 2) + /* ap1 maybe in {sp1, n + 1} */ + /* bp1 maybe in {sp1 + n + 1, n + 1} */ + + { + mp_srcptr am1, bm1; + mp_size_t anm, bnm; + mp_ptr so; + + bm1 = b0; + bnm = bn; + if (LIKELY (an > n)) + { + am1 = xp; + cy = mpn_add (xp, a0, n, a1, an - n); + MPN_INCR_U (xp, n, cy); + anm = n; + so = xp + n; + if (LIKELY (bn > n)) + { + bm1 = so; + cy = mpn_add (so, b0, n, b1, bn - n); + MPN_INCR_U (so, n, cy); + bnm = n; + so += n; + } + } + else + { + so = xp; + am1 = a0; + anm = an; + } + + mpn_mulmod_bnm1 (rp, n, am1, anm, bm1, bnm, so); + } + + { + int k; + mp_srcptr ap1, bp1; + mp_size_t anp, bnp; + + bp1 = b0; + bnp = bn; + if (LIKELY (an > n)) { + ap1 = sp1; + cy = mpn_sub (sp1, a0, n, a1, an - n); + sp1[n] = 0; + MPN_INCR_U (sp1, n + 1, cy); + anp = n + ap1[n]; + if (LIKELY (bn > n)) { + bp1 = sp1 + n + 1; + cy = mpn_sub (sp1 + n + 1, b0, n, b1, bn - n); + sp1[2*n+1] = 0; + MPN_INCR_U (sp1 + n + 1, n + 1, cy); + bnp = n + bp1[n]; + } + } else { + ap1 = a0; + anp = an; + } + + if (BELOW_THRESHOLD (n, MUL_FFT_MODF_THRESHOLD)) + k=0; + else + { + int mask; + k = mpn_fft_best_k (n, 0); + mask = (1<>=1;}; + } + if (k >= FFT_FIRST_K) + xp[n] = mpn_mul_fft (xp, n, ap1, anp, bp1, bnp, k); + else if (UNLIKELY (bp1 == b0)) + { + ASSERT (anp + bnp <= 2*n+1); + ASSERT (anp + bnp > n); + ASSERT (anp >= bnp); + mpn_mul (xp, ap1, anp, bp1, bnp); + anp = anp + bnp - n; + ASSERT (anp <= n || xp[2*n]==0); + anp-= anp > n; + cy = mpn_sub (xp, xp, n, xp + n, anp); + xp[n] = 0; + MPN_INCR_U (xp, n+1, cy); + } + else + mpn_bc_mulmod_bnp1 (xp, ap1, bp1, n, xp); + } + + /* Here the CRT recomposition begins. + + xm <- (xp + xm)/2 = (xp + xm)B^n/2 mod (B^n-1) + Division by 2 is a bitwise rotation. + + Assumes xp normalised mod (B^n+1). + + The residue class [0] is represented by [B^n-1]; except when + both input are ZERO. + */ + +#if HAVE_NATIVE_mpn_rsh1add_n || HAVE_NATIVE_mpn_rsh1add_nc +#if HAVE_NATIVE_mpn_rsh1add_nc + cy = mpn_rsh1add_nc(rp, rp, xp, n, xp[n]); /* B^n = 1 */ + hi = cy << (GMP_NUMB_BITS - 1); + cy = 0; + /* next update of rp[n-1] will set cy = 1 only if rp[n-1]+=hi + overflows, i.e. a further increment will not overflow again. */ +#else /* ! _nc */ + cy = xp[n] + mpn_rsh1add_n(rp, rp, xp, n); /* B^n = 1 */ + hi = (cy<<(GMP_NUMB_BITS-1))&GMP_NUMB_MASK; /* (cy&1) << ... */ + cy >>= 1; + /* cy = 1 only if xp[n] = 1 i.e. {xp,n} = ZERO, this implies that + the rsh1add was a simple rshift: the top bit is 0. cy=1 => hi=0. */ +#endif +#if GMP_NAIL_BITS == 0 + add_ssaaaa(cy, rp[n-1], cy, rp[n-1], 0, hi); +#else + cy += (hi & rp[n-1]) >> (GMP_NUMB_BITS-1); + rp[n-1] ^= hi; +#endif +#else /* ! HAVE_NATIVE_mpn_rsh1add_n */ +#if HAVE_NATIVE_mpn_add_nc + cy = mpn_add_nc(rp, rp, xp, n, xp[n]); +#else /* ! _nc */ + cy = xp[n] + mpn_add_n(rp, rp, xp, n); /* xp[n] == 1 implies {xp,n} == ZERO */ +#endif + cy += (rp[0]&1); + mpn_rshift(rp, rp, n, 1); + ASSERT (cy <= 2); + hi = (cy<<(GMP_NUMB_BITS-1))&GMP_NUMB_MASK; /* (cy&1) << ... */ + cy >>= 1; + /* We can have cy != 0 only if hi = 0... */ + ASSERT ((rp[n-1] & GMP_NUMB_HIGHBIT) == 0); + rp[n-1] |= hi; + /* ... rp[n-1] + cy can not overflow, the following INCR is correct. */ +#endif + ASSERT (cy <= 1); + /* Next increment can not overflow, read the previous comments about cy. */ + ASSERT ((cy == 0) || ((rp[n-1] & GMP_NUMB_HIGHBIT) == 0)); + MPN_INCR_U(rp, n, cy); + + /* Compute the highest half: + ([(xp + xm)/2 mod (B^n-1)] - xp ) * B^n + */ + if (UNLIKELY (an + bn < rn)) + { + /* Note that in this case, the only way the result can equal + zero mod B^{rn} - 1 is if one of the inputs is zero, and + then the output of both the recursive calls and this CRT + reconstruction is zero, not B^{rn} - 1. Which is good, + since the latter representation doesn't fit in the output + area.*/ + cy = mpn_sub_n (rp + n, rp, xp, an + bn - n); + + /* FIXME: This subtraction of the high parts is not really + necessary, we do it to get the carry out, and for sanity + checking. */ + cy = xp[n] + mpn_sub_nc (xp + an + bn - n, rp + an + bn - n, + xp + an + bn - n, rn - (an + bn), cy); + ASSERT (an + bn == rn - 1 || + mpn_zero_p (xp + an + bn - n + 1, rn - 1 - (an + bn))); + cy = mpn_sub_1 (rp, rp, an + bn, cy); + ASSERT (cy == (xp + an + bn - n)[0]); + } + else + { + cy = xp[n] + mpn_sub_n (rp + n, rp, xp, n); + /* cy = 1 only if {xp,n+1} is not ZERO, i.e. {rp,n} is not ZERO. + DECR will affect _at most_ the lowest n limbs. */ + MPN_DECR_U (rp, 2*n, cy); + } +#undef a0 +#undef a1 +#undef b0 +#undef b1 +#undef xp +#undef sp1 + } +} + +mp_size_t +mpn_mulmod_bnm1_next_size (mp_size_t n) +{ + mp_size_t nh; + + if (BELOW_THRESHOLD (n, MULMOD_BNM1_THRESHOLD)) + return n; + if (BELOW_THRESHOLD (n, 4 * (MULMOD_BNM1_THRESHOLD - 1) + 1)) + return (n + (2-1)) & (-2); + if (BELOW_THRESHOLD (n, 8 * (MULMOD_BNM1_THRESHOLD - 1) + 1)) + return (n + (4-1)) & (-4); + + nh = (n + 1) >> 1; + + if (BELOW_THRESHOLD (nh, MUL_FFT_MODF_THRESHOLD)) + return (n + (8-1)) & (-8); + + return 2 * mpn_fft_next_size (nh, mpn_fft_best_k (nh, 0)); +} -- cgit v1.2.3