zgetc2(3)

NAME

ZGETC2 - compute an LU factorization, using complete piv

oting, of the n-by-n matrix A

SYNOPSIS

SUBROUTINE ZGETC2( N, A, LDA, IPIV, JPIV, INFO )
    INTEGER        INFO, LDA, N
    INTEGER        IPIV( * ), JPIV( * )
    COMPLEX*16     A( LDA, * )

PURPOSE

ZGETC2 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 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*16 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 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

ZGETC2(3)