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/*=============================================================================
This file is part of FLINT.
FLINT is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
FLINT is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with FLINT; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2008-2011 William Hart
******************************************************************************/
#include <stdlib.h>
#include "fmpz_poly.h"
#include "fft.h"
#include "fft_tuning.h"
void _fmpz_poly_mullow_SS(fmpz * output, const fmpz * input1, slong len1,
const fmpz * input2, slong len2, slong trunc)
{
slong len_out, loglen, loglen2, n;
slong output_bits, limbs, size, i;
mp_limb_t * ptr, * t1, * t2, * tt, * s1, ** ii, ** jj;
slong bits1, bits2;
ulong size1, size2;
int sign = 0;
len1 = FLINT_MIN(len1, trunc);
len2 = FLINT_MIN(len2, trunc);
len_out = len1 + len2 - 1;
loglen = FLINT_CLOG2(len_out);
loglen2 = FLINT_CLOG2(len2);
n = (WORD(1) << (loglen - 2));
size1 = _fmpz_vec_max_limbs(input1, len1);
size2 = _fmpz_vec_max_limbs(input2, len2);
/* Start with an upper bound on the number of bits needed */
output_bits = FLINT_BITS * (size1 + size2) + loglen2 + 1;
/* round up for sqrt2 trick */
output_bits = (((output_bits - 1) >> (loglen - 2)) + 1) << (loglen - 2);
limbs = (output_bits - 1) / FLINT_BITS + 1; /* initial size of FFT coeffs */
if (limbs > FFT_MULMOD_2EXPP1_CUTOFF) /* can't be worse than next power of 2 limbs */
limbs = (WORD(1) << FLINT_CLOG2(limbs));
size = limbs + 1;
/* allocate space for ffts */
ii = flint_malloc((4*(n + n*size) + 5*size)*sizeof(mp_limb_t));
for (i = 0, ptr = (mp_limb_t *) ii + 4*n; i < 4*n; i++, ptr += size)
ii[i] = ptr;
t1 = ptr;
t2 = t1 + size;
s1 = t2 + size;
tt = s1 + size;
if (input1 != input2)
{
jj = flint_malloc(4*(n + n*size)*sizeof(mp_limb_t));
for (i = 0, ptr = (mp_limb_t *) jj + 4*n; i < 4*n; i++, ptr += size)
jj[i] = ptr;
} else jj = ii;
/* put coefficients into FFT vecs */
bits1 = _fmpz_vec_get_fft(ii, input1, limbs, len1);
for (i = len1; i < 4*n; i++)
flint_mpn_zero(ii[i], limbs + 1);
if (input1 != input2)
{
bits2 = _fmpz_vec_get_fft(jj, input2, limbs, len2);
for (i = len2; i < 4*n; i++)
flint_mpn_zero(jj[i], limbs + 1);
}
else bits2 = bits1;
if (bits1 < WORD(0) || bits2 < WORD(0))
{
sign = 1;
bits1 = FLINT_ABS(bits1);
bits2 = FLINT_ABS(bits2);
}
/* Recompute the number of bits/limbs now that we know how large everything is */
output_bits = bits1 + bits2 + loglen2 + sign;
/* round up output bits for sqrt2 */
output_bits = (((output_bits - 1) >> (loglen - 2)) + 1) << (loglen - 2);
limbs = (output_bits - 1) / FLINT_BITS + 1;
limbs = fft_adjust_limbs(limbs); /* round up limbs for Nussbaumer */
fft_convolution(ii, jj, loglen - 2, limbs, len_out, &t1, &t2, &s1, tt);
_fmpz_vec_set_fft(output, trunc, ii, limbs, sign); /* write output */
flint_free(ii);
if (input1 != input2)
flint_free(jj);
}
void
fmpz_poly_mullow_SS(fmpz_poly_t res,
const fmpz_poly_t poly1, const fmpz_poly_t poly2, slong n)
{
const slong len1 = poly1->length;
const slong len2 = poly2->length;
if (len1 == 0 || len2 == 0 || n == 0)
{
fmpz_poly_zero(res);
return;
}
if (len1 <= 2 || len2 <= 2 || n <= 2)
{
fmpz_poly_mullow_classical(res, poly1, poly2, n);
return;
}
n = FLINT_MIN(n, len1 + len2 - 1);
fmpz_poly_fit_length(res, n);
if (len1 >= len2)
_fmpz_poly_mullow_SS(res->coeffs, poly1->coeffs, len1,
poly2->coeffs, len2, n);
else
_fmpz_poly_mullow_SS(res->coeffs, poly2->coeffs, len2,
poly1->coeffs, len1, n);
_fmpz_poly_set_length(res, n);
_fmpz_poly_normalise(res);
}
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