+++ /dev/null
-/* mpn_jacobi_base -- limb/limb Jacobi symbol with restricted arguments.
-
- THIS INTERFACE IS PRELIMINARY AND MIGHT DISAPPEAR OR BE SUBJECT TO
- INCOMPATIBLE CHANGES IN A FUTURE RELEASE OF GMP. */
-
-/*
-Copyright (C) 1999, 2000 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 the GNU Lesser General Public License as published by
-the Free Software Foundation; either version 2.1 of the License, or (at your
-option) any later version.
-
-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 Lesser General Public
-License for more details.
-
-You should have received a copy of the GNU Lesser General Public License
-along with the GNU MP Library; see the file COPYING.LIB. If not, write to
-the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
-MA 02111-1307, USA. */
-
-#include "gmp.h"
-#include "gmp-impl.h"
-#include "longlong.h"
-
-
-#if COUNT_TRAILING_ZEROS_TIME <= 7
-/* If count_trailing_zeros is fast, use it.
- K7 at 7 cycles and P6 at 2 are good here. K6 at 12-27 and P5 at 18-42
- are not. The default 15 in longlong.h is meant to mean not good here. */
-
-#define PROCESS_TWOS_ANY \
- { \
- mp_limb_t twos; \
- count_trailing_zeros (twos, a); \
- result_bit1 ^= JACOBI_TWOS_U_BIT1 (twos, b); \
- a >>= twos; \
- }
-
-#define PROCESS_TWOS_EVEN PROCESS_TWOS_ANY
-
-#else
-/* Use a loop instead. With "a" uniformly distributed there will usually be
- only a few trailing zeros.
-
- Unfortunately the branch for the while loop here will be on a 50/50
- chance of a 1 or 0, which is bad for branch prediction. */
-
-#define PROCESS_TWOS_EVEN \
- { \
- int two; \
- two = JACOBI_TWO_U_BIT1 (b); \
- do \
- { \
- a >>= 1; \
- result_bit1 ^= two; \
- ASSERT (a != 0); \
- } \
- while ((a & 1) == 0); \
- }
-
-#define PROCESS_TWOS_ANY \
- if ((a & 1) == 0) \
- PROCESS_TWOS_EVEN;
-
-#endif
-
-
-/* Calculate the value of the Jacobi symbol (a/b) of two mp_limb_t's, but
- with a restricted range of inputs accepted, namely b>1, b odd, and a<=b.
-
- The initial result_bit1 is taken as a parameter for the convenience of
- mpz_kronecker_zi_ui() et al. The sign changes both here and in those
- routines accumulate nicely in bit 1, see the JACOBI macros.
-
- The return value here is the normal +1, 0, or -1. Note that +1 and -1
- have bit 1 in the "BIT1" sense, which could be useful if the caller is
- accumulating it into some extended calculation.
-
- Duplicating the loop body to avoid the MP_LIMB_T_SWAP(a,b) would be
- possible, but a couple of tests suggest it's not a significant speedup,
- and may even be a slowdown, so what's here is good enough for now.
-
- Future: The code doesn't demand a<=b actually, so maybe this could be
- relaxed. All the places this is used currently call with a<=b though. */
-
-int
-#if __STDC__
-mpn_jacobi_base (mp_limb_t a, mp_limb_t b, int result_bit1)
-#else
-mpn_jacobi_base (a, b, result_bit1)
- mp_limb_t a;
- mp_limb_t b;
- int result_bit1;
-#endif
-{
- ASSERT (b & 1); /* b odd */
- ASSERT (b != 1);
- ASSERT (a <= b);
-
- if (a == 0)
- return 0;
-
- PROCESS_TWOS_ANY;
- if (a == 1)
- goto done;
-
- for (;;)
- {
- result_bit1 ^= JACOBI_RECIP_UU_BIT1 (a, b);
- MP_LIMB_T_SWAP (a, b);
-
- do
- {
- /* working on (a/b), a,b odd, a>=b */
- ASSERT (a & 1);
- ASSERT (b & 1);
- ASSERT (a >= b);
-
- if ((a -= b) == 0)
- return 0;
-
- PROCESS_TWOS_EVEN;
- if (a == 1)
- goto done;
- }
- while (a >= b);
- }
-
- done:
- return JACOBI_BIT1_TO_PN (result_bit1);
-}
projects / ghc-hetmet.git / blobdiff