Return to kronzu.c CVS log

Up to [local] / OpenXM_contrib / gmp / mpz

Annotation of OpenXM_contrib/gmp/mpz/kronzu.c, Revision 1.1.1.1

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: }