143 lines
4.6 KiB
C
143 lines
4.6 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) 2008-2011 William Hart
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******************************************************************************/
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#include <stdlib.h>
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#include "fmpz_poly.h"
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#include "fft.h"
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#include "fft_tuning.h"
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void _fmpz_poly_mullow_SS(fmpz * output, const fmpz * input1, slong len1,
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const fmpz * input2, slong len2, slong trunc)
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{
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slong len_out = len1 + len2 - 1;
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slong loglen = FLINT_CLOG2(len_out);
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slong loglen2 = FLINT_CLOG2(len2);
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slong n = (WORD(1) << (loglen - 2));
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slong output_bits, limbs, size, i;
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mp_limb_t * ptr, * t1, * t2, * tt, * s1, ** ii, ** jj;
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slong bits1, bits2;
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int sign = 0;
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ulong size1 = _fmpz_vec_max_limbs(input1, len1);
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ulong size2 = _fmpz_vec_max_limbs(input2, len2);
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/* Start with an upper bound on the number of bits needed */
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output_bits = FLINT_BITS * (size1 + size2) + loglen2 + 1;
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/* round up for sqrt2 trick */
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output_bits = (((output_bits - 1) >> (loglen - 2)) + 1) << (loglen - 2);
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limbs = (output_bits - 1) / FLINT_BITS + 1; /* initial size of FFT coeffs */
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if (limbs > FFT_MULMOD_2EXPP1_CUTOFF) /* can't be worse than next power of 2 limbs */
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limbs = (WORD(1) << FLINT_CLOG2(limbs));
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size = limbs + 1;
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/* allocate space for ffts */
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ii = flint_malloc((4*(n + n*size) + 5*size)*sizeof(mp_limb_t));
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for (i = 0, ptr = (mp_limb_t *) ii + 4*n; i < 4*n; i++, ptr += size)
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ii[i] = ptr;
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t1 = ptr;
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t2 = t1 + size;
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s1 = t2 + size;
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tt = s1 + size;
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if (input1 != input2)
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{
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jj = flint_malloc(4*(n + n*size)*sizeof(mp_limb_t));
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for (i = 0, ptr = (mp_limb_t *) jj + 4*n; i < 4*n; i++, ptr += size)
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jj[i] = ptr;
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} else jj = ii;
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/* put coefficients into FFT vecs */
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bits1 = _fmpz_vec_get_fft(ii, input1, limbs, len1);
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for (i = len1; i < 4*n; i++)
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flint_mpn_zero(ii[i], limbs + 1);
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if (input1 != input2)
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{
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bits2 = _fmpz_vec_get_fft(jj, input2, limbs, len2);
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for (i = len2; i < 4*n; i++)
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flint_mpn_zero(jj[i], limbs + 1);
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}
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else bits2 = bits1;
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if (bits1 < WORD(0) || bits2 < WORD(0))
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{
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sign = 1;
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bits1 = FLINT_ABS(bits1);
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bits2 = FLINT_ABS(bits2);
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}
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/* Recompute the number of bits/limbs now that we know how large everything is */
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output_bits = bits1 + bits2 + loglen2 + sign;
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/* round up output bits for sqrt2 */
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output_bits = (((output_bits - 1) >> (loglen - 2)) + 1) << (loglen - 2);
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limbs = (output_bits - 1) / FLINT_BITS + 1;
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limbs = fft_adjust_limbs(limbs); /* round up limbs for Nussbaumer */
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fft_convolution(ii, jj, loglen - 2, limbs, len_out, &t1, &t2, &s1, tt);
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_fmpz_vec_set_fft(output, trunc, ii, limbs, sign); /* write output */
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flint_free(ii);
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if (input1 != input2)
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flint_free(jj);
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}
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void
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fmpz_poly_mullow_SS(fmpz_poly_t res,
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const fmpz_poly_t poly1, const fmpz_poly_t poly2, slong n)
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{
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const slong len1 = poly1->length;
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const slong len2 = poly2->length;
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if (len1 == 0 || len2 == 0 || n == 0)
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{
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fmpz_poly_zero(res);
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return;
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}
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if (len1 == 1 || len2 == 1)
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{
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fmpz_poly_mullow_classical(res, poly1, poly2, n);
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return;
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}
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fmpz_poly_fit_length(res, n);
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if (len1 >= len2)
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_fmpz_poly_mullow_SS(res->coeffs, poly1->coeffs, len1,
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poly2->coeffs, len2, n);
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else
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_fmpz_poly_mullow_SS(res->coeffs, poly2->coeffs, len2,
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poly1->coeffs, len1, n);
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_fmpz_poly_set_length(res, n);
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_fmpz_poly_normalise(res);
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}
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