93 lines
2.6 KiB
C
93 lines
2.6 KiB
C
/*=============================================================================
|
|
|
|
This file is part of FLINT.
|
|
|
|
FLINT is free software; you can redistribute it and/or modify
|
|
it under the terms of the GNU General Public License as published by
|
|
the Free Software Foundation; either version 2 of the License, or
|
|
(at your option) any later version.
|
|
|
|
FLINT is distributed in the hope that it will be useful,
|
|
but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
|
|
GNU General Public License for more details.
|
|
|
|
You should have received a copy of the GNU General Public License
|
|
along with FLINT; if not, write to the Free Software
|
|
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
|
|
|
|
=============================================================================*/
|
|
/******************************************************************************
|
|
|
|
Copyright (C) 2013 Mike Hansen
|
|
|
|
******************************************************************************/
|
|
|
|
#include <stdio.h>
|
|
#include <string.h>
|
|
|
|
#include "fq.h"
|
|
#include "fq_poly.h"
|
|
|
|
void
|
|
fq_ctx_init_modulus(fq_ctx_t ctx, fmpz_mod_poly_t modulus, const char *var)
|
|
{
|
|
slong nz;
|
|
int i, j;
|
|
fmpz* p;
|
|
fmpz_t inv;
|
|
|
|
p = &(modulus->p);
|
|
|
|
/* Count number of nonzero coefficients */
|
|
nz = 0;
|
|
for (i = 0; i < modulus->length; i++)
|
|
{
|
|
if (!fmpz_is_zero(modulus->coeffs + i))
|
|
{
|
|
nz += 1;
|
|
}
|
|
}
|
|
|
|
ctx->len = nz;
|
|
ctx->a = _fmpz_vec_init(ctx->len);
|
|
ctx->j = flint_malloc(ctx->len * sizeof(slong));
|
|
|
|
fmpz_init(inv);
|
|
fmpz_invmod(inv, modulus->coeffs + modulus->length - 1, p);
|
|
|
|
/* Copy the polynomial */
|
|
j = 0;
|
|
for (i = 0; i < modulus->length; i++)
|
|
{
|
|
if (!fmpz_is_zero(modulus->coeffs + i))
|
|
{
|
|
fmpz_mul(ctx->a + j, inv, modulus->coeffs + i);
|
|
fmpz_mod(ctx->a + j, ctx->a + j, p);
|
|
ctx->j[j] = i;
|
|
j++;
|
|
}
|
|
}
|
|
|
|
fmpz_clear(inv);
|
|
|
|
if (ctx->len < 6)
|
|
ctx->sparse_modulus = 1;
|
|
else
|
|
ctx->sparse_modulus = 0;
|
|
|
|
fmpz_init_set(fq_ctx_prime(ctx), p);
|
|
|
|
ctx->var = flint_malloc(strlen(var) + 1);
|
|
strcpy(ctx->var, var);
|
|
|
|
/* Set the modulus */
|
|
fmpz_mod_poly_init(ctx->modulus, fq_ctx_prime(ctx));
|
|
fmpz_mod_poly_set(ctx->modulus, modulus);
|
|
|
|
/* Precompute the inverse of the modulus */
|
|
fmpz_mod_poly_init(ctx->inv, fq_ctx_prime(ctx));
|
|
fmpz_mod_poly_reverse(ctx->inv, ctx->modulus, ctx->modulus->length);
|
|
fmpz_mod_poly_inv_series_newton(ctx->inv, ctx->inv, ctx->modulus->length);
|
|
}
|