81 lines
2.2 KiB
C
81 lines
2.2 KiB
C
/* mpz_kronecker_ui -- mpz+ulong Kronecker/Jacobi symbol.
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Copyright 1999, 2000, 2001, 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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#include "gmp.h"
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#include "gmp-impl.h"
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#include "longlong.h"
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int
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mpz_kronecker_ui (mpz_srcptr a, unsigned long b)
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{
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mp_srcptr a_ptr;
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mp_size_t a_size;
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mp_limb_t a_rem;
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int result_bit1;
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a_size = SIZ(a);
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if (a_size == 0)
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return JACOBI_0U (b);
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if (b > GMP_NUMB_MAX)
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{
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mp_limb_t blimbs[2];
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mpz_t bz;
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ALLOC(bz) = numberof (blimbs);
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PTR(bz) = blimbs;
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mpz_set_ui (bz, b);
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return mpz_kronecker (a, bz);
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}
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a_ptr = PTR(a);
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if ((b & 1) != 0)
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{
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result_bit1 = JACOBI_ASGN_SU_BIT1 (a_size, b);
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}
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else
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{
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mp_limb_t a_low = a_ptr[0];
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int twos;
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if (b == 0)
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return JACOBI_LS0 (a_low, a_size); /* (a/0) */
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if (! (a_low & 1))
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return 0; /* (even/even)=0 */
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/* (a/2)=(2/a) for a odd */
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count_trailing_zeros (twos, b);
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b >>= twos;
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result_bit1 = (JACOBI_TWOS_U_BIT1 (twos, a_low)
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^ JACOBI_ASGN_SU_BIT1 (a_size, b));
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}
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if (b == 1)
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return JACOBI_BIT1_TO_PN (result_bit1); /* (a/1)=1 for any a */
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a_size = ABS(a_size);
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/* (a/b) = (a mod b / b) */
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JACOBI_MOD_OR_MODEXACT_1_ODD (result_bit1, a_rem, a_ptr, a_size, b);
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return mpn_jacobi_base (a_rem, (mp_limb_t) b, result_bit1);
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}
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