98 lines
2.9 KiB
C
98 lines
2.9 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) 2012 Sebastian Pancratz
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******************************************************************************/
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#include "qadic.h"
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/*
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Forms the product of (op1,len1) and (op2,len2) modulo (a,j,lena) and pN.
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Assumes that len1 >= len2 > 0. Requires rop to be of size at least
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len1 + len2 - 1.
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*/
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static
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void _qadic_mul(fmpz *rop,
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const fmpz *op1, slong len1, const fmpz *op2, slong len2,
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const fmpz *a, const slong *j, slong lena, const fmpz_t pN)
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{
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_fmpz_poly_mul(rop, op1, len1, op2, len2);
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_fmpz_mod_poly_reduce(rop, len1 + len2 - 1, a, j, lena, pN);
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}
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void qadic_mul(qadic_t x, const qadic_t y, const qadic_t z,
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const qadic_ctx_t ctx)
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{
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const slong leny = y->length;
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const slong lenz = z->length;
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const slong lenx = leny + lenz - 1;
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const slong N = qadic_prec(x);
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const slong d = qadic_ctx_degree(ctx);
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if (leny == 0 || lenz == 0 || y->val + z->val >= N)
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{
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qadic_zero(x);
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}
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else
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{
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fmpz *t;
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fmpz_t pN;
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int alloc;
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x->val = y->val + z->val;
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alloc = _padic_ctx_pow_ui(pN, N - x->val, &ctx->pctx);
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if (x == y || x == z)
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{
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t = _fmpz_vec_init(lenx);
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}
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else
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{
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padic_poly_fit_length(x, lenx);
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t = x->coeffs;
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}
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if (leny >= lenz)
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_qadic_mul(t, y->coeffs, leny,
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z->coeffs, lenz, ctx->a, ctx->j, ctx->len, pN);
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else
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_qadic_mul(t, z->coeffs, lenz,
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y->coeffs, leny, ctx->a, ctx->j, ctx->len, pN);
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if (x == y || x == z)
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{
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_fmpz_vec_clear(x->coeffs, x->alloc);
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x->coeffs = t;
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x->alloc = lenx;
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}
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_padic_poly_set_length(x, FLINT_MIN(lenx, d));
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_padic_poly_normalise(x);
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if (alloc)
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fmpz_clear(pN);
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}
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}
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