108 lines
3.2 KiB
C
108 lines
3.2 KiB
C
/*=============================================================================
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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) 2010 Fredrik Johansson
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******************************************************************************/
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#include <stdlib.h>
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#include <gmp.h>
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#include "flint.h"
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#include "fmpz.h"
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#include "mpn_extras.h"
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mp_size_t flint_mpn_remove_power_ascending(mp_ptr x, mp_size_t xsize,
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mp_ptr p, mp_size_t psize, ulong *exp)
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{
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int i, maxi;
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mp_ptr div;
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mp_ptr rem;
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mp_ptr square[FLINT_BITS];
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mp_size_t square_size[FLINT_BITS];
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mp_size_t sqsize;
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*exp = 0;
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if (psize > xsize)
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return xsize;
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maxi = 0;
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square[0] = p;
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square_size[0] = psize;
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/* Most likely less memory will be needed, but this way we
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avoid reallocations */
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div = flint_malloc(sizeof(mp_limb_t) * xsize);
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rem = flint_malloc(sizeof(mp_limb_t) * xsize);
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/* Remove ascending powers */
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for (i = 0; i < FLINT_BITS && xsize >= square_size[i]; i++)
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{
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mpn_tdiv_qr(div, rem, 0, x, xsize, square[i], square_size[i]);
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if (!flint_mpn_zero_p(rem, square_size[i]))
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{
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i -= 1;
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break;
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}
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*exp += (1 << i);
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xsize = xsize - square_size[i] + 1;
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if (div[xsize-1] == 0)
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xsize--;
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flint_mpn_copyi(x, div, xsize);
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/* Form next square if needed */
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sqsize = square_size[i] * 2;
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if (sqsize - 1 > xsize)
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break;
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maxi = i + 1;
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square[i + 1] = flint_malloc(sizeof(mp_limb_t) * sqsize);
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mpn_sqr(square[i + 1], square[i], square_size[i]);
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if (square[i + 1][sqsize - 1] == 0)
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sqsize -= 1;
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square_size[i + 1] = sqsize;
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}
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/* Remove descending powers */
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for ( ; i >= 0; i--)
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{
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if (xsize >= square_size[i])
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{
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mpn_tdiv_qr(div, rem, 0, x, xsize, square[i], square_size[i]);
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if (flint_mpn_zero_p(rem, square_size[i]))
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{
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*exp += (1 << i);
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xsize = xsize - square_size[i] + 1;
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if (div[xsize-1] == 0)
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xsize--;
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flint_mpn_copyi(x, div, xsize);
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}
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}
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}
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for (i = 1; i <= maxi; i++)
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flint_free(square[i]);
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flint_free(div);
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flint_free(rem);
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return xsize;
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}
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