171 lines
7.5 KiB
C
171 lines
7.5 KiB
C
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/* Alternate implementations of modlimb_invert to compare speeds. */
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/*
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Copyright 2000, 2002 Free Software Foundation, Inc.
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This file is part of the GNU MP Library.
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The GNU MP Library is free software; you can redistribute it and/or modify
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it under the terms of the GNU Lesser General Public License as published by
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the Free Software Foundation; either version 2.1 of the License, or (at your
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option) any later version.
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The GNU MP Library is distributed in the hope that it will be useful, but
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WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
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or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
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License for more details.
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You should have received a copy of the GNU Lesser General Public License
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along with the GNU MP Library; see the file COPYING.LIB. If not, write to
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the Free Software Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
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MA 02110-1301, USA.
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*/
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#include <stdio.h>
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#include "gmp.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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#include "speed.h"
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/* Like the standard version in gmp-impl.h, but with the expressions using a
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"1-" form. This has the same number of steps, but "1-" is on the
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dependent chain, whereas the "2*" in the standard version isn't.
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Depending on the CPU this should be the same or a touch slower. */
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#if BITS_PER_MP_LIMB <= 32
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#define modlimb_invert_mul1(inv,n) \
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do { \
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mp_limb_t __n = (n); \
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mp_limb_t __inv; \
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ASSERT ((__n & 1) == 1); \
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__inv = modlimb_invert_table[(__n&0xFF)/2]; /* 8 */ \
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__inv = (1 - __n * __inv) * __inv + __inv; /* 16 */ \
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__inv = (1 - __n * __inv) * __inv + __inv; /* 32 */ \
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ASSERT (__inv * __n == 1); \
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(inv) = __inv; \
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} while (0)
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#endif
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#if BITS_PER_MP_LIMB > 32 && BITS_PER_MP_LIMB <= 64
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#define modlimb_invert_mul1(inv,n) \
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do { \
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mp_limb_t __n = (n); \
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mp_limb_t __inv; \
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ASSERT ((__n & 1) == 1); \
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__inv = modlimb_invert_table[(__n&0xFF)/2]; /* 8 */ \
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__inv = (1 - __n * __inv) * __inv + __inv; /* 16 */ \
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__inv = (1 - __n * __inv) * __inv + __inv; /* 32 */ \
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__inv = (1 - __n * __inv) * __inv + __inv; /* 64 */ \
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ASSERT (__inv * __n == 1); \
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(inv) = __inv; \
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} while (0)
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#endif
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/* The loop based version used in GMP 3.0 and earlier. Usually slower than
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multiplying, due to the number of steps that must be performed. Much
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slower when the processor has a good multiply. */
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#define modlimb_invert_loop(inv,n) \
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do { \
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mp_limb_t __v = (n); \
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mp_limb_t __v_orig = __v; \
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mp_limb_t __make_zero = 1; \
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mp_limb_t __two_i = 1; \
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mp_limb_t __v_inv = 0; \
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\
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ASSERT ((__v & 1) == 1); \
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\
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do \
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{ \
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while ((__two_i & __make_zero) == 0) \
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__two_i <<= 1, __v <<= 1; \
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__v_inv += __two_i; \
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__make_zero -= __v; \
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} \
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while (__make_zero); \
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\
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ASSERT (__v_orig * __v_inv == 1); \
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(inv) = __v_inv; \
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} while (0)
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/* Another loop based version with conditionals, but doing a fixed number of
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steps. */
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#define modlimb_invert_cond(inv,n) \
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do { \
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mp_limb_t __n = (n); \
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mp_limb_t __rem = (1 - __n) >> 1; \
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mp_limb_t __inv = GMP_LIMB_HIGHBIT; \
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int __count; \
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\
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ASSERT ((__n & 1) == 1); \
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\
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__count = BITS_PER_MP_LIMB-1; \
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do \
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{ \
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__inv >>= 1; \
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if (__rem & 1) \
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{ \
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__inv |= GMP_LIMB_HIGHBIT; \
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__rem -= __n; \
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} \
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__rem >>= 1; \
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} \
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while (-- __count); \
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\
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ASSERT (__inv * __n == 1); \
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(inv) = __inv; \
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} while (0)
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/* Another loop based bitwise version, but purely arithmetic, no
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conditionals. */
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#define modlimb_invert_arith(inv,n) \
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do { \
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mp_limb_t __n = (n); \
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mp_limb_t __rem = (1 - __n) >> 1; \
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mp_limb_t __inv = GMP_LIMB_HIGHBIT; \
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mp_limb_t __lowbit; \
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int __count; \
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\
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ASSERT ((__n & 1) == 1); \
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\
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__count = BITS_PER_MP_LIMB-1; \
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do \
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{ \
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__lowbit = __rem & 1; \
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__inv = (__inv >> 1) | (__lowbit << (BITS_PER_MP_LIMB-1)); \
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__rem = (__rem - (__n & -__lowbit)) >> 1; \
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} \
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while (-- __count); \
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\
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ASSERT (__inv * __n == 1); \
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(inv) = __inv; \
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} while (0)
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double
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speed_modlimb_invert_mul1 (struct speed_params *s)
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{
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SPEED_ROUTINE_MODLIMB_INVERT (modlimb_invert_mul1);
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}
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double
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speed_modlimb_invert_loop (struct speed_params *s)
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{
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SPEED_ROUTINE_MODLIMB_INVERT (modlimb_invert_loop);
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}
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double
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speed_modlimb_invert_cond (struct speed_params *s)
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{
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SPEED_ROUTINE_MODLIMB_INVERT (modlimb_invert_cond);
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}
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double
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speed_modlimb_invert_arith (struct speed_params *s)
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{
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SPEED_ROUTINE_MODLIMB_INVERT (modlimb_invert_arith);
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}
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