121 lines
3.2 KiB
C
121 lines
3.2 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) 2010 William Hart
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Copyright (C) 2011 Sebastian Pancratz
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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 "fmpz_vec.h"
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#include "fmpz_poly.h"
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#include "ulong_extras.h"
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/*
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For documentation, see fmpz_poly/mul_karatsuba.c
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*/
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extern void revbin1(fmpz * out, const fmpz * in, slong len, slong bits);
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extern void revbin2(fmpz * out, const fmpz * in, slong len, slong bits);
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extern void _fmpz_vec_add_rev(fmpz * in1, fmpz * in2, slong bits);
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void _fmpz_poly_sqr_kara_recursive(fmpz * out, fmpz * rev,
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fmpz * temp, slong bits)
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{
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slong len = (WORD(1) << bits);
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slong m = len / 2;
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if (len == 1)
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{
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fmpz_mul(out, rev, rev);
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fmpz_zero(out + 1);
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return;
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}
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_fmpz_vec_add(temp, rev, rev + m, m);
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_fmpz_poly_sqr_kara_recursive(out, rev, temp + 2 * m, bits - 1);
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_fmpz_poly_sqr_kara_recursive(out + len, temp, temp + 2 * m, bits - 1);
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_fmpz_poly_sqr_kara_recursive(temp, rev + m, temp + 2 * m, bits - 1);
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_fmpz_vec_sub(out + len, out + len, out, len);
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_fmpz_vec_sub(out + len, out + len, temp, len);
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_fmpz_vec_add_rev(out, temp, bits);
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}
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void _fmpz_poly_sqr_karatsuba(fmpz * res, const fmpz * poly, slong len)
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{
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fmpz *rev, *out, *temp;
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slong length, loglen = 0;
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if (len == 1)
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{
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fmpz_mul(res, poly, poly);
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return;
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}
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while ((WORD(1) << loglen) < len)
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loglen++;
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length = (WORD(1) << loglen);
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rev = flint_calloc(3 * length, sizeof(fmpz *));
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out = rev + length;
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temp = _fmpz_vec_init(2 * length);
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revbin1(rev, poly, len, loglen);
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_fmpz_poly_sqr_kara_recursive(out, rev, temp, loglen);
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_fmpz_vec_zero(res, 2 * len - 1);
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revbin2(res, out, 2 * len - 1, loglen + 1);
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_fmpz_vec_clear(temp, 2 * length);
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flint_free(rev);
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}
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void fmpz_poly_sqr_karatsuba(fmpz_poly_t res, const fmpz_poly_t poly)
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{
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slong len;
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if (poly->length == 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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len = 2 * poly->length - 1;
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fmpz_poly_fit_length(res, len);
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_fmpz_poly_sqr_karatsuba(res->coeffs, poly->coeffs, poly->length);
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_fmpz_poly_set_length(res, len);
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}
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