arb/acb_dirichlet/vec_nth_root.c
2016-09-06 14:37:14 +02:00

105 lines
2.9 KiB
C

/*=============================================================================
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) 2016 Pascal Molin
******************************************************************************/
#include "acb_dirichlet.h"
/* assume xs has size >= len * step */
void
_acb_vec_set_powers_step(acb_ptr xs, slong n, slong len, slong step, slong prec)
{
slong i, j;
prec += n_clog(n, 2);
for (i = 0, j = 0; i < len; i++, j += step)
{
if (i == 0)
acb_one(xs + j);
else if (i == 1)
acb_dirichlet_nth_root(xs + j, n, prec);
else if (i % 2 == 0)
acb_mul(xs + j, xs + j / 2, xs + j / 2, prec);
else
acb_mul(xs + j, xs + j - step, xs + step, prec);
}
}
/* assume len = p^e and z has size >= len * step */
void
_acb_vec_roots_pe(acb_ptr z, slong p, slong e, slong len, slong step, slong prec)
{
if (e <= 1)
{
_acb_vec_set_powers_step(z, p, len, step, prec);
}
else
{
slong q, r;
_acb_vec_roots_pe(z, p, e - 1, len / p, step * p, prec);
_acb_vec_set_powers_step(z, n_pow(p, e), p, step, prec);
for (q = p; q < len; q += p)
for (r = 1; r < p; r++)
acb_mul(z + (q + r) * step, z + q * step, z + r * step, prec);
}
}
void
acb_dirichlet_vec_nth_roots(acb_ptr z, slong len, slong prec)
{
slong i, q;
n_factor_t fac;
acb_one(z + 0);
n_factor_init(&fac);
n_factor(&fac, len, 0);
q = 1;
for (i = 0; i < fac.num; i++)
{
slong p, e, pe, mp, mq;
p = fac.p[i];
e = fac.exp[i];
pe = n_pow(p, e);
mp = len / pe;
mq = len / q;
_acb_vec_roots_pe(z, p, e, pe, mp, prec);
if (i > 0)
{
slong k, l;
for (k = mp; k < len; k += mp)
{
for (l = mq; l < len - k; l += mq)
acb_mul(z + k + l, z + k, z + l, prec);
for (; l < len; l += mq)
acb_mul(z + k + l - len, z + k, z + l, prec);
}
}
q *= pe;
}
}