CGETC2 - compute an LU factorization, using complete piv
oting, 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 pivot
ing, 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 diagonal ele
ments 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 factors L and U from the factorization A
= P*L*U*Q; the unit diagonal 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 non
singular 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.
Based on contributions by
Bo Kagstrom and Peter Poromaa, Department of Computing
Science,
Umea University, S-901 87 Umea, Sweden.
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