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/*
Copyright (C) 2012 Fredrik Johansson
This file is part of FLINT.
FLINT is free software: you can redistribute it and/or modify it under
the terms of the GNU Lesser General Public License (LGPL) as published
by the Free Software Foundation; either version 3 of the License, or
(at your option) any later version. See <https://www.gnu.org/licenses/>.
*/
#include <math.h>
#include "arb_poly.h"
void
_arb_poly_mullow(arb_ptr res,
arb_srcptr poly1, slong len1,
arb_srcptr poly2, slong len2, slong n, slong prec)
{
if (n == 1)
{
arb_mul(res, poly1, poly2, prec);
}
else if (n <= 7 || len1 <= 7 || len2 <= 7)
{
_arb_poly_mullow_classical(res, poly1, len1, poly2, len2, n, prec);
}
else
{
slong cutoff;
double p;
if (prec <= 2 * FLINT_BITS)
{
cutoff = 110;
}
else
{
p = log(prec);
cutoff = 10000.0 / (p * p * p);
cutoff = FLINT_MIN(cutoff, 60);
if (poly1 == poly2 && prec >= 256)
cutoff *= 1.25;
if (poly1 == poly2 && prec >= 4096)
cutoff *= 1.25;
cutoff = FLINT_MAX(cutoff, 8);
}
if (2 * FLINT_MIN(len1, len2) <= cutoff || n <= cutoff)
_arb_poly_mullow_classical(res, poly1, len1, poly2, len2, n, prec);
else
_arb_poly_mullow_block(res, poly1, len1, poly2, len2, n, prec);
}
}
void
arb_poly_mullow(arb_poly_t res, const arb_poly_t poly1,
const arb_poly_t poly2, slong n, slong prec)
{
slong len1, len2;
len1 = poly1->length;
len2 = poly2->length;
if (len1 == 0 || len2 == 0 || n == 0)
{
arb_poly_zero(res);
return;
}
n = FLINT_MIN((len1 + len2 - 1), n);
len1 = FLINT_MIN(len1, n);
len2 = FLINT_MIN(len2, n);
/* Hack to avoid temporary allocations with first derivatives. */
if (n <= 2 && !(len1 == 2 && len2 == 2))
{
arb_poly_fit_length(res, n);
if (n == 1)
{
arb_mul(res->coeffs, poly1->coeffs, poly2->coeffs, prec);
}
else if (len2 == 1)
{
arb_mul(res->coeffs + 1, poly1->coeffs + 1, poly2->coeffs, prec);
arb_mul(res->coeffs, poly1->coeffs, poly2->coeffs, prec);
}
else if (len1 == 1)
{
arb_mul(res->coeffs + 1, poly2->coeffs + 1, poly1->coeffs, prec);
arb_mul(res->coeffs, poly2->coeffs, poly1->coeffs, prec);
}
else
{
flint_throw(FLINT_ERROR, "(%s)\n", __func__);
#if 0
if (res == poly1 || res == poly2)
{
arb_t t;
arb_init(t);
arb_mul(t, poly1->coeffs, poly2->coeffs + 1, prec);
arb_addmul(t, poly2->coeffs, poly1->coeffs + 1, prec);
arb_mul(res->coeffs, poly1->coeffs, poly2->coeffs, prec);
arb_swap(t, res->coeffs + 1);
arb_clear(t);
}
else
{
arb_mul(res->coeffs, poly1->coeffs, poly2->coeffs, prec);
arb_mul(res->coeffs + 1, poly1->coeffs, poly2->coeffs + 1, prec);
arb_addmul(res->coeffs + 1, poly2->coeffs, poly1->coeffs + 1, prec);
}
#endif
}
_arb_poly_set_length(res, n);
_arb_poly_normalise(res);
return;
}
if (res == poly1 || res == poly2)
{
arb_poly_t t;
arb_poly_init2(t, n);
_arb_poly_mullow(t->coeffs, poly1->coeffs, len1,
poly2->coeffs, len2, n, prec);
arb_poly_swap(res, t);
arb_poly_clear(t);
}
else
{
arb_poly_fit_length(res, n);
_arb_poly_mullow(res->coeffs, poly1->coeffs, len1,
poly2->coeffs, len2, n, prec);
}
_arb_poly_set_length(res, n);
_arb_poly_normalise(res);
}