Annotation of OpenXM_contrib/gmp/mpz/kronzu.c, Revision 1.1
1.1 ! maekawa 1: /* mpz_kronecker_ui -- Kronecker/Jacobi symbol. */
! 2:
! 3: /*
! 4: Copyright (C) 1999, 2000 Free Software Foundation, Inc.
! 5:
! 6: This file is part of the GNU MP Library.
! 7:
! 8: The GNU MP Library is free software; you can redistribute it and/or modify
! 9: it under the terms of the GNU Lesser General Public License as published by
! 10: the Free Software Foundation; either version 2.1 of the License, or (at your
! 11: option) any later version.
! 12:
! 13: The GNU MP Library is distributed in the hope that it will be useful, but
! 14: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
! 15: or FITNESS FOR A PARTICULAR PURPOSE. See the GNU Lesser General Public
! 16: License for more details.
! 17:
! 18: You should have received a copy of the GNU Lesser General Public License
! 19: along with the GNU MP Library; see the file COPYING.LIB. If not, write to
! 20: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
! 21: MA 02111-1307, USA.
! 22: */
! 23:
! 24: #include "gmp.h"
! 25: #include "gmp-impl.h"
! 26: #include "longlong.h"
! 27:
! 28:
! 29: /* This function is expected to be often used with b an odd prime, so the
! 30: code for odd b is nice and short. */
! 31:
! 32: int
! 33: #if __STDC__
! 34: mpz_kronecker_ui (mpz_srcptr a, unsigned long b)
! 35: #else
! 36: mpz_kronecker_ui (a, b)
! 37: mpz_srcptr a;
! 38: unsigned long b;
! 39: #endif
! 40: {
! 41: int twos;
! 42:
! 43: if (b & 1)
! 44: {
! 45: if (b != 1)
! 46: return mpn_jacobi_base (mpz_fdiv_ui (a, b), b, 0);
! 47: else
! 48: return 1; /* (a/1)=1 for any a */
! 49: }
! 50:
! 51: if (b == 0)
! 52: return JACOBI_Z0 (a);
! 53:
! 54: /* (a/2)=0 if a even */
! 55: if (mpz_even_p (a))
! 56: return 0;
! 57:
! 58: /* (a/2)=(2/a) when a odd */
! 59: count_trailing_zeros (twos, b);
! 60: b >>= twos;
! 61: if (b == 1)
! 62: return JACOBI_TWOS_U (twos, PTR(a)[0]);
! 63:
! 64: return mpn_jacobi_base (mpz_fdiv_ui (a, b), b,
! 65: JACOBI_TWOS_U_BIT1(twos, PTR(a)[0]));
! 66: }
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