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/*============================================================================
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) 2012 Sebastian Pancratz
******************************************************************************/
#include "fmpz_mod_poly.h"
#include "padic_poly.h"
/*
TODO: Move this bit of code into "padic".
*/
static void __padic_reduce(fmpz_t u, slong *v, slong N, const padic_ctx_t ctx)
{
if (!fmpz_is_zero(u))
{
if (*v < N)
{
int alloc;
fmpz_t pow;
alloc = _padic_ctx_pow_ui(pow, N - *v, ctx);
fmpz_mod(u, u, pow);
if (alloc)
fmpz_clear(pow);
}
else
{
fmpz_zero(u);
*v = 0;
}
}
}
/* Assumes that len1 > 0. */
void _padic_poly_compose(fmpz *rop, slong *rval, slong N,
const fmpz *op1, slong val1, slong len1,
const fmpz *op2, slong val2, slong len2,
const padic_ctx_t ctx)
{
const slong lenr = (len1 - 1) * (len2 - 1) + 1;
if (len1 == 1 || len2 == 0)
{
fmpz_set(rop, op1);
*rval = val1;
__padic_reduce(rop, rval, N, ctx);
}
else if (val2 >= 0)
{
if (val1 >= N)
{
_fmpz_vec_zero(rop, lenr);
*rval = 0;
}
else
{
fmpz *vec2;
fmpz_t f;
fmpz_t pow;
int alloc;
vec2 = _fmpz_vec_init(len2);
fmpz_init(f);
fmpz_pow_ui(f, ctx->p, val2);
_fmpz_vec_scalar_mul_fmpz(vec2, op2, len2, f);
alloc = _padic_ctx_pow_ui(pow, N - val1, ctx);
_fmpz_mod_poly_compose(rop, op1, len1, vec2, len2, pow);
*rval= val1;
_padic_poly_canonicalise(rop, rval, lenr, ctx->p);
_fmpz_vec_clear(vec2, len2);
fmpz_clear(f);
if (alloc)
fmpz_clear(pow);
}
}
else /* val2 < 0 */
{
const slong n = len1 - 1;
if (val1 + n*val2 >= N)
{
_fmpz_vec_zero(rop, lenr);
*rval = 0;
}
else
{
fmpz_t pow;
int alloc;
fmpz *vec1;
fmpz_t s, t;
slong i;
vec1 = _fmpz_vec_init(len1);
fmpz_init(s);
fmpz_init(t);
alloc = _padic_ctx_pow_ui(pow, N - val1 - n*val2, ctx);
fmpz_pow_ui(s, ctx->p, -val2);
fmpz_one(t);
fmpz_set(vec1 + (len1 - 1), op1 + (len1 - 1));
for (i = len1 - 2; i >= 0; i--)
{
fmpz_mul(t, t, s);
fmpz_mul(vec1 + i, op1 + i, t);
}
_fmpz_mod_poly_compose(rop, vec1, len1, op2, len2, pow);
*rval = val1 + n*val2;
_padic_poly_canonicalise(rop, rval, lenr, ctx->p);
_fmpz_vec_clear(vec1, len1);
fmpz_clear(s);
fmpz_clear(t);
if (alloc)
fmpz_clear(pow);
}
}
}
void padic_poly_compose(padic_poly_t rop,
const padic_poly_t op1, const padic_poly_t op2,
const padic_ctx_t ctx)
{
const slong len1 = op1->length, len2 = op2->length;
if (len1 == 0)
{
padic_poly_zero(rop);
}
else if (len1 == 1 || len2 == 0)
{
padic_poly_fit_length(rop, 1);
fmpz_set(rop->coeffs, op1->coeffs);
rop->val = op1->val;
_padic_poly_set_length(rop, 1);
padic_poly_canonicalise(rop, ctx->p);
padic_poly_reduce(rop, ctx);
}
else
{
const slong lenr = (len1 - 1) * (len2 - 1) + 1;
if (rop != op1 && rop != op2)
{
padic_poly_fit_length(rop, lenr);
_padic_poly_compose(rop->coeffs, &(rop->val), rop->N,
op1->coeffs, op1->val, op1->length,
op2->coeffs, op2->val, op2->length, ctx);
_padic_poly_set_length(rop, lenr);
}
else
{
fmpz *t = _fmpz_vec_init(lenr);
_padic_poly_compose(t, &(rop->val), rop->N,
op1->coeffs, op1->val, op1->length,
op2->coeffs, op2->val, op2->length, ctx);
_fmpz_vec_clear(rop->coeffs, rop->alloc);
rop->coeffs = t;
rop->alloc = lenr;
rop->length = lenr;
}
_padic_poly_normalise(rop);
}
}
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