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qr.c
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qr.c
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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) 2014 Abhinav Baid
******************************************************************************/
#include "mpf_mat.h"
void
mpf_mat_qr(mpf_mat_t Q, mpf_mat_t R, const mpf_mat_t A)
{
slong i, j, k;
int flag, orig;
mpf_t t, s, tmp, eps;
mp_bitcnt_t exp;
if (Q->r != A->r || Q->c != A->c || R->r != A->c || R->c != A->c)
{
flint_printf("Exception (mpf_mat_qr). Incompatible dimensions.\n");
abort();
}
if (Q == A)
{
mpf_mat_t T;
mpf_mat_init(T, A->r, A->c, Q->prec);
mpf_mat_qr(T, R, A);
mpf_mat_swap(Q, T);
mpf_mat_clear(T);
return;
}
if (A->r == 0)
{
return;
}
mpf_init2(t, Q->prec);
mpf_init2(s, Q->prec);
mpf_init2(tmp, Q->prec);
mpf_init2(eps, Q->prec);
exp = ceil((A->prec) / 64.0) * 64;
flint_mpf_set_ui(eps, 1);
mpf_div_2exp(eps, eps, exp);
for (k = 0; k < A->c; k++)
{
for (j = 0; j < A->r; j++)
{
mpf_set(mpf_mat_entry(Q, j, k), mpf_mat_entry(A, j, k));
}
orig = flag = 1;
while (flag)
{
flint_mpf_set_ui(t, 0);
for (i = 0; i < k; i++)
{
flint_mpf_set_ui(s, 0);
for (j = 0; j < A->r; j++)
{
mpf_mul(tmp, mpf_mat_entry(Q, j, i),
mpf_mat_entry(Q, j, k));
mpf_add(s, s, tmp);
}
if (orig)
{
mpf_set(mpf_mat_entry(R, i, k), s);
}
else
{
mpf_add(mpf_mat_entry(R, i, k), mpf_mat_entry(R, i, k), s);
}
mpf_mul(tmp, s, s);
mpf_add(t, t, tmp);
for (j = 0; j < A->r; j++)
{
mpf_mul(tmp, s, mpf_mat_entry(Q, j, i));
mpf_sub(mpf_mat_entry(Q, j, k), mpf_mat_entry(Q, j, k),
tmp);
}
}
flint_mpf_set_ui(s, 0);
for (j = 0; j < A->r; j++)
{
mpf_mul(tmp, mpf_mat_entry(Q, j, k), mpf_mat_entry(Q, j, k));
mpf_add(s, s, tmp);
}
mpf_add(t, t, s);
flag = 0;
if (mpf_cmp(s, t) < 0)
{
orig = 0;
if (mpf_cmp(s, eps) < 0)
flint_mpf_set_ui(s, 0);
else
flag = 1;
}
}
mpf_sqrt(s, s);
mpf_set(mpf_mat_entry(R, k, k), s);
if (flint_mpf_cmp_ui(s, 0) != 0)
mpf_ui_div(s, 1, s);
for (j = 0; j < A->r; j++)
{
mpf_mul(mpf_mat_entry(Q, j, k), mpf_mat_entry(Q, j, k), s);
}
}
mpf_clears(t, s, tmp, eps, NULL);
}