arb/fmpcb_mat/lu.c
2012-11-07 16:07:22 +01:00

87 lines
2.2 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) 2012 Fredrik Johansson
******************************************************************************/
#include "fmpcb_mat.h"
int
fmpcb_mat_lu(long * P, fmpcb_mat_t LU, const fmpcb_mat_t A, long prec)
{
fmpcb_t d, e;
fmpcb_struct ** a;
long i, j, m, n, r, row, col;
int result;
m = fmpcb_mat_nrows(A);
n = fmpcb_mat_ncols(A);
result = 1;
if (m == 0 || n == 0)
return result;
fmpcb_mat_set(LU, A);
a = LU->rows;
row = col = 0;
for (i = 0; i < m; i++)
P[i] = i;
fmpcb_init(d);
fmpcb_init(e);
while (row < m && col < n)
{
r = fmpcb_mat_find_pivot_partial(LU, row, m, col);
if (r == -1)
{
result = 0;
break;
}
else if (r != row)
fmpcb_mat_swap_rows(LU, P, row, r);
fmpcb_set(d, a[row] + col);
for (j = row + 1; j < m; j++)
{
fmpcb_div(e, a[j] + col, d, prec);
fmpcb_neg(e, e);
_fmpcb_vec_scalar_addmul(a[j] + col,
a[row] + col, n - col, e, prec);
fmpcb_zero(a[j] + col);
fmpcb_neg(a[j] + row, e);
}
row++;
col++;
}
fmpcb_clear(d);
fmpcb_clear(e);
return result;
}