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Annotation of OpenXM_contrib/gmp/mpz/kronzu.c, Revision 1.1.1.2

1.1.1.2 ! ohara       1: /* mpz_kronecker_ui -- mpz+ulong Kronecker/Jacobi symbol.
1.1       maekawa     2:
1.1.1.2 ! ohara       3: Copyright 1999, 2000, 2001, 2002 Free Software Foundation, Inc.
1.1       maekawa     4:
                      5: This file is part of the GNU MP Library.
                      6:
                      7: The GNU MP Library is free software; you can redistribute it and/or modify
                      8: it under the terms of the GNU Lesser General Public License as published by
                      9: the Free Software Foundation; either version 2.1 of the License, or (at your
                     10: option) any later version.
                     11:
                     12: The GNU MP Library is distributed in the hope that it will be useful, but
                     13: WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
                     14: or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU Lesser General Public
                     15: License for more details.
                     16:
                     17: You should have received a copy of the GNU Lesser General Public License
                     18: along with the GNU MP Library; see the file COPYING.LIB.  If not, write to
                     19: the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston,
1.1.1.2 ! ohara      20: MA 02111-1307, USA. */
1.1       maekawa    21:
                     22: #include "gmp.h"
                     23: #include "gmp-impl.h"
                     24: #include "longlong.h"
                     25:
                     26:
1.1.1.2 ! ohara      27: /* This implementation depends on BITS_PER_MP_LIMB being even, so that
        !            28:    (a/2)^BITS_PER_MP_LIMB = 1 and so there's no need to pay attention to how
        !            29:    many low zero limbs are stripped.  */
        !            30: #if BITS_PER_MP_LIMB % 2 != 0
        !            31: Error, error, unsupported BITS_PER_MP_LIMB
        !            32: #endif
        !            33:
1.1       maekawa    34:
                     35: int
                     36: mpz_kronecker_ui (mpz_srcptr a, unsigned long b)
                     37: {
1.1.1.2 ! ohara      38:   mp_srcptr  a_ptr = PTR(a);
        !            39:   mp_size_t  a_size;
        !            40:   mp_limb_t  a_rem;
        !            41:   int        result_bit1;
        !            42:
        !            43:   a_size = SIZ(a);
        !            44:   if (a_size == 0)
        !            45:     return JACOBI_0U (b);
1.1       maekawa    46:
1.1.1.2 ! ohara      47:   if (b > GMP_NUMB_MAX)
1.1       maekawa    48:     {
1.1.1.2 ! ohara      49:       mp_limb_t  blimbs[2];
        !            50:       mpz_t      bz;
        !            51:       ALLOC(bz) = numberof (blimbs);
        !            52:       PTR(bz) = blimbs;
        !            53:       mpz_set_ui (bz, b);
        !            54:       return mpz_kronecker (a, bz);
1.1       maekawa    55:     }
                     56:
1.1.1.2 ! ohara      57:   if ((b & 1) != 0)
        !            58:     {
        !            59:       result_bit1 = JACOBI_ASGN_SU_BIT1 (a_size, b);
        !            60:     }
        !            61:   else
        !            62:     {
        !            63:       mp_limb_t  a_low = a_ptr[0];
        !            64:       int        twos;
        !            65:
        !            66:       if (b == 0)
        !            67:         return JACOBI_LS0 (a_low, a_size);   /* (a/0) */
        !            68:
        !            69:       if (! (a_low & 1))
        !            70:         return 0;  /* (even/even)=0 */
        !            71:
        !            72:       /* (a/2)=(2/a) for a odd */
        !            73:       count_trailing_zeros (twos, b);
        !            74:       b >>= twos;
        !            75:       result_bit1 = (JACOBI_TWOS_U_BIT1 (twos, a_low)
        !            76:                      ^ JACOBI_ASGN_SU_BIT1 (a_size, b));
        !            77:     }
1.1       maekawa    78:
                     79:   if (b == 1)
1.1.1.2 ! ohara      80:     return JACOBI_BIT1_TO_PN (result_bit1);  /* (a/1)=1 for any a */
        !            81:
        !            82:   a_size = ABS(a_size);
1.1       maekawa    83:
1.1.1.2 ! ohara      84:   /* (a/b) = (a mod b / b) */
        !            85:   JACOBI_MOD_OR_MODEXACT_1_ODD (result_bit1, a_rem, a_ptr, a_size, b);
        !            86:   return mpn_jacobi_base (a_rem, (mp_limb_t) b, result_bit1);
1.1       maekawa    87: }