118 lines
3.6 KiB
C
118 lines
3.6 KiB
C
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/*
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Copyright 2009, 2011 William Hart. All rights reserved.
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Redistribution and use in source and binary forms, with or without modification, are
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permitted provided that the following conditions are met:
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1. Redistributions of source code must retain the above copyright notice, this list of
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conditions and the following disclaimer.
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2. Redistributions in binary form must reproduce the above copyright notice, this list
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of conditions and the following disclaimer in the documentation and/or other materials
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provided with the distribution.
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THIS SOFTWARE IS PROVIDED BY William Hart ``AS IS'' AND ANY EXPRESS OR IMPLIED
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WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL William Hart OR
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CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR
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SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
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NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF
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ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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The views and conclusions contained in the software and documentation are those of the
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authors and should not be interpreted as representing official policies, either expressed
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or implied, of 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 "fft.h"
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void fft_butterfly_sqrt2(mp_limb_t * s, mp_limb_t * t,
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mp_limb_t * i1, mp_limb_t * i2, mp_size_t i,
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mp_size_t limbs, mp_bitcnt_t w, mp_limb_t * temp)
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{
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mp_bitcnt_t wn = limbs*FLINT_BITS;
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mp_limb_t cy = 0;
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mp_size_t j = i/2, k = w/2;
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mp_size_t y;
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mp_bitcnt_t b1;
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int negate = 0;
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b1 = j + wn/4 + i*k;
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if (b1 >= wn)
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{
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negate = 1;
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b1 -= wn;
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}
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y = b1/FLINT_BITS;
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b1 = b1%FLINT_BITS;
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/* sumdiff and multiply by 2^{j + wn/4 + i*k} */
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butterfly_lshB(s, t, i1, i2, limbs, 0, y);
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mpn_mul_2expmod_2expp1(t, t, limbs, b1);
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/* multiply by 2^{wn/2} */
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y = limbs/2;
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flint_mpn_copyi(temp + y, t, limbs - y);
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temp[limbs] = 0;
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if (y) cy = mpn_neg_n(temp, t + limbs - y, y);
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mpn_addmod_2expp1_1(temp + y, limbs - y, -t[limbs]);
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mpn_sub_1(temp + y, temp + y, limbs - y + 1, cy);
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/* shift by an additional half limb (rare) */
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if (limbs & 1)
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mpn_mul_2expmod_2expp1(temp, temp, limbs, FLINT_BITS/2);
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/* subtract */
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if (negate)
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mpn_sub_n(t, t, temp, limbs + 1);
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else
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mpn_sub_n(t, temp, t, limbs + 1);
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}
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void fft_truncate_sqrt2(mp_limb_t ** ii, mp_size_t n, mp_bitcnt_t w,
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mp_limb_t ** t1, mp_limb_t ** t2, mp_limb_t ** temp, mp_size_t trunc)
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{
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mp_size_t i;
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mp_size_t limbs = (w*n)/GMP_LIMB_BITS;
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if ((w & 1) == 0)
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{
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fft_truncate(ii, 2*n, w/2, t1, t2, trunc);
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return;
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}
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for (i = 0; i < trunc - 2*n; i++)
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{
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fft_butterfly(*t1, *t2, ii[i], ii[2*n+i], i/2, limbs, w);
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SWAP_PTRS(ii[i], *t1);
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SWAP_PTRS(ii[i+2*n], *t2);
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i++;
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fft_butterfly_sqrt2(*t1, *t2, ii[i], ii[2*n+i], i, limbs, w, *temp);
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SWAP_PTRS(ii[i], *t1);
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SWAP_PTRS(ii[2*n+i], *t2);
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}
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for (i = trunc - 2*n; i < 2*n; i++)
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{
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fft_adjust(ii[i+2*n], ii[i], i/2, limbs, w);
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i++;
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fft_adjust_sqrt2(ii[i+2*n], ii[i], i, limbs, w, *temp);
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}
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fft_radix2(ii, n, w, t1, t2);
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fft_truncate1(ii + 2*n, n, w, t1, t2, trunc - 2*n);
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}
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