93 lines
2.6 KiB
C
93 lines
2.6 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) 2013 Mike Hansen
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******************************************************************************/
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#include <stdio.h>
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#include <string.h>
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#include "fq.h"
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#include "fq_poly.h"
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void
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fq_ctx_init_modulus(fq_ctx_t ctx, fmpz_mod_poly_t modulus, const char *var)
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{
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slong nz;
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int i, j;
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fmpz* p;
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fmpz_t inv;
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p = &(modulus->p);
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/* Count number of nonzero coefficients */
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nz = 0;
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for (i = 0; i < modulus->length; i++)
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{
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if (!fmpz_is_zero(modulus->coeffs + i))
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{
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nz += 1;
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}
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}
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ctx->len = nz;
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ctx->a = _fmpz_vec_init(ctx->len);
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ctx->j = flint_malloc(ctx->len * sizeof(slong));
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fmpz_init(inv);
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fmpz_invmod(inv, modulus->coeffs + modulus->length - 1, p);
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/* Copy the polynomial */
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j = 0;
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for (i = 0; i < modulus->length; i++)
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{
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if (!fmpz_is_zero(modulus->coeffs + i))
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{
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fmpz_mul(ctx->a + j, inv, modulus->coeffs + i);
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fmpz_mod(ctx->a + j, ctx->a + j, p);
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ctx->j[j] = i;
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j++;
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}
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}
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fmpz_clear(inv);
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if (ctx->len < 6)
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ctx->sparse_modulus = 1;
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else
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ctx->sparse_modulus = 0;
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fmpz_init_set(fq_ctx_prime(ctx), p);
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ctx->var = flint_malloc(strlen(var) + 1);
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strcpy(ctx->var, var);
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/* Set the modulus */
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fmpz_mod_poly_init(ctx->modulus, fq_ctx_prime(ctx));
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fmpz_mod_poly_set(ctx->modulus, modulus);
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/* Precompute the inverse of the modulus */
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fmpz_mod_poly_init(ctx->inv, fq_ctx_prime(ctx));
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fmpz_mod_poly_reverse(ctx->inv, ctx->modulus, ctx->modulus->length);
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fmpz_mod_poly_inv_series_newton(ctx->inv, ctx->inv, ctx->modulus->length);
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}
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