124 lines
3.2 KiB
C
124 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 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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void
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_fmpz_poly_pow_binomial(fmpz * res, const fmpz * poly, ulong e)
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{
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ulong i, f;
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fmpz_t a, b, c;
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*a = WORD(1);
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*b = WORD(1);
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*c = WORD(1);
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fmpz_one(res);
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fmpz_one(res + e);
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for (i = UWORD(1), f = e - UWORD(1); i <= (e - UWORD(1)) >> 1; i++, f--)
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{
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fmpz_mul(a, a, poly);
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fmpz_mul(b, b, poly + 1);
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fmpz_mul_ui(c, c, f + UWORD(1));
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fmpz_divexact_ui(c, c, i);
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fmpz_mul(res + i, b, c);
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fmpz_mul(res + f, a, c);
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}
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if ((e & UWORD(1)) == UWORD(0))
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{
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fmpz_mul(a, a, poly);
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fmpz_mul(b, b, poly + 1);
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fmpz_mul_ui(c, c, f + UWORD(1));
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fmpz_divexact_ui(c, c, i);
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fmpz_mul(res + i, b, c);
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fmpz_mul(res + i, res + i, a);
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i++, f--;
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}
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for ( ; i <= e; i++, f--)
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{
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fmpz_mul(a, a, poly);
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fmpz_mul(b, b, poly + 1);
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fmpz_mul(res + i, res + i, b);
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fmpz_mul(res + f, res + f, a);
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}
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fmpz_clear(a);
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fmpz_clear(b);
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fmpz_clear(c);
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}
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void
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fmpz_poly_pow_binomial(fmpz_poly_t res, const fmpz_poly_t poly, ulong e)
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{
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const slong len = poly->length;
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slong rlen;
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if (len != 2)
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{
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flint_printf("Exception (fmpz_poly_pow_binomial). poly->length not equal to 2.\n");
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abort();
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}
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if (e < UWORD(3))
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{
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if (e == UWORD(0))
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fmpz_poly_set_ui(res, UWORD(1));
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else if (e == UWORD(1))
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fmpz_poly_set(res, poly);
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else /* e == UWORD(2) */
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fmpz_poly_sqr(res, poly);
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return;
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}
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rlen = (slong) e + 1;
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if (res != poly)
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{
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fmpz_poly_fit_length(res, rlen);
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_fmpz_poly_set_length(res, rlen);
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_fmpz_poly_pow_binomial(res->coeffs, poly->coeffs, e);
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}
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else
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{
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fmpz_poly_t t;
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fmpz_poly_init2(t, rlen);
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_fmpz_poly_set_length(t, rlen);
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_fmpz_poly_pow_binomial(t->coeffs, poly->coeffs, e);
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fmpz_poly_swap(res, t);
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fmpz_poly_clear(t);
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}
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}
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