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/*
Copyright (C) 2012 Fredrik Johansson
This file is part of Arb.
Arb 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 2.1 of the License, or
(at your option) any later version. See <http://www.gnu.org/licenses/>.
*/
#include "acb_mat.h"
int
acb_cmpabs_approx(const acb_t x, const acb_t y)
{
const arf_struct *xm, *ym;
if (arf_cmpabs(arb_midref(acb_realref(x)), arb_midref(acb_imagref(x))) >= 0)
xm = arb_midref(acb_realref(x));
else
xm = arb_midref(acb_imagref(x));
if (arf_cmpabs(arb_midref(acb_realref(y)), arb_midref(acb_imagref(y))) >= 0)
ym = arb_midref(acb_realref(y));
else
ym = arb_midref(acb_imagref(y));
return arf_cmpabs(xm, ym);
}
slong
acb_mat_find_pivot_partial(const acb_mat_t mat,
slong start_row, slong end_row, slong c)
{
slong best_row, i;
best_row = -1;
for (i = start_row; i < end_row; i++)
{
if (!acb_contains_zero(acb_mat_entry(mat, i, c)))
{
if (best_row == -1)
{
best_row = i;
}
/* todo: should take the radius into account */
else if (acb_cmpabs_approx(acb_mat_entry(mat, i, c), acb_mat_entry(mat, best_row, c)) > 0)
{
best_row = i;
}
}
}
return best_row;
}
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