CGETC2(l) ) CGETC2(l)NAME
CGETC2 - compute an LU factorization, using complete pivoting, of the
n-by-n matrix A
SYNOPSIS
SUBROUTINE CGETC2( N, A, LDA, IPIV, JPIV, INFO )
INTEGER INFO, LDA, N
INTEGER IPIV( * ), JPIV( * )
COMPLEX A( LDA, * )
PURPOSE
CGETC2 computes an LU factorization, using complete pivoting, of the n-
by-n matrix A. The factorization has the form A = P * L * U * Q, where
P and Q are permutation matrices, L is lower triangular with unit diag‐
onal elements and U is upper triangular.
This is a level 1 BLAS version of the algorithm.
ARGUMENTS
N (input) INTEGER
The order of the matrix A. N >= 0.
A (input/output) COMPLEX array, dimension (LDA, N)
On entry, the n-by-n matrix to be factored. On exit, the fac‐
tors L and U from the factorization A = P*L*U*Q; the unit diag‐
onal elements of L are not stored. If U(k, k) appears to be
less than SMIN, U(k, k) is given the value of SMIN, giving a
nonsingular perturbed system.
LDA (input) INTEGER
The leading dimension of the array A. LDA >= max(1, N).
IPIV (output) INTEGER array, dimension (N).
The pivot indices; for 1 <= i <= N, row i of the matrix has
been interchanged with row IPIV(i).
JPIV (output) INTEGER array, dimension (N).
The pivot indices; for 1 <= j <= N, column j of the matrix has
been interchanged with column JPIV(j).
INFO (output) INTEGER
= 0: successful exit
> 0: if INFO = k, U(k, k) is likely to produce overflow if one
tries to solve for x in Ax = b. So U is perturbed to avoid the
overflow.
FURTHER DETAILS
Based on contributions by
Bo Kagstrom and Peter Poromaa, Department of Computing Science,
Umea University, S-901 87 Umea, Sweden.
LAPACK version 3.0 15 June 2000 CGETC2(l)
