arb/fmprb_poly/revert_series.c

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/*=============================================================================
This file is part of ARB.
ARB 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.
ARB 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 ARB; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
=============================================================================*/
/******************************************************************************
Copyright (C) 2013 Fredrik Johansson
******************************************************************************/
#include "fmprb_poly.h"
void
_fmprb_poly_revert_series(fmprb_ptr Qinv,
fmprb_srcptr Q, long n, long prec)
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{
_fmprb_poly_revert_series_lagrange_fast(Qinv, Q, n, prec);
}
void
fmprb_poly_revert_series(fmprb_poly_t Qinv,
const fmprb_poly_t Q, long n, long prec)
{
fmprb_ptr Qcopy;
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int Qalloc;
long Qlen = Q->length;
if (Q->length < 2 || !fmprb_is_zero(Q->coeffs)
|| fmprb_contains_zero(Q->coeffs + 1))
{
printf("Exception (fmprb_poly_revert_series). Input must \n"
"have zero constant term and nonzero coefficient of x^1.\n");
abort();
}
if (n < 2)
{
fmprb_poly_zero(Qinv);
return;
}
if (Qlen >= n)
{
Qcopy = Q->coeffs;
Qalloc = 0;
}
else
{
long i;
Qcopy = _fmprb_vec_init(n);
for (i = 0; i < Qlen; i++)
Qcopy[i] = Q->coeffs[i];
Qalloc = 1;
}
if (Qinv != Q)
{
fmprb_poly_fit_length(Qinv, n);
_fmprb_poly_revert_series(Qinv->coeffs, Qcopy, n, prec);
}
else
{
fmprb_poly_t t;
fmprb_poly_init2(t, n);
_fmprb_poly_revert_series(t->coeffs, Qcopy, n, prec);
fmprb_poly_swap(Qinv, t);
fmprb_poly_clear(t);
}
_fmprb_poly_set_length(Qinv, n);
_fmprb_poly_normalise(Qinv);
if (Qalloc)
flint_free(Qcopy);
}