71 lines
2.2 KiB
C
71 lines
2.2 KiB
C
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/*=============================================================================
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This file is part of FLINT.
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FLINT is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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FLINT is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with FLINT; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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=============================================================================*/
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/******************************************************************************
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Copyright (C) 2013 William Hart
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******************************************************************************/
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#include <gmp.h>
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#include "flint.h"
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#include "ulong_extras.h"
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#include "mpn_extras.h"
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#include "fmpz.h"
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void fmpz_preinvn_init(fmpz_preinvn_t inv, fmpz_t f)
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{
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fmpz c = *f;
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mp_bitcnt_t norm;
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mp_ptr t;
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if (c == 0)
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{
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flint_printf("Exception (fmpz_preinvn_init). Division by zero.\n");
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abort();
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} else if (!COEFF_IS_MPZ(c)) /* c is small */
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{
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inv->dinv = flint_malloc(sizeof(mp_limb_t));
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if (c < 0) c = -c;
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count_leading_zeros(norm, c);
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if (norm) c <<= norm;
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flint_mpn_preinvn(inv->dinv, (mp_ptr) &c, 1);
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inv->n = 1;
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} else /* c is big */
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{
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__mpz_struct * mpz_ptr = COEFF_TO_PTR(c);
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slong size = FLINT_ABS(mpz_ptr->_mp_size);
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inv->dinv = flint_malloc(size*sizeof(mp_limb_t));
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count_leading_zeros(norm, mpz_ptr->_mp_d[size - 1]);
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if (norm)
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{
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t = flint_malloc(size*sizeof(mp_limb_t));
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mpn_lshift(t, mpz_ptr->_mp_d, size, norm);
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} else
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t = mpz_ptr->_mp_d;
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flint_mpn_preinvn(inv->dinv, t, size);
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inv->n = size;
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if (norm) flint_free(t);
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}
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inv->norm = norm;
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}
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