sgetc2(3)

NAME

SGETC2 - compute an LU factorization with complete pivot

ing of the n-by-n matrix A

SYNOPSIS

SUBROUTINE SGETC2( N, A, LDA, IPIV, JPIV, INFO )
    INTEGER        INFO, LDA, N
    INTEGER        IPIV( * ), JPIV( * )
    REAL           A( LDA, * )

PURPOSE

SGETC2 computes an LU factorization with 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 tri

angular with unit diagonal elements and U is upper triangular.

This is the Level 2 BLAS algorithm.

ARGUMENTS

N (input) INTEGER

The order of the matrix A. N >= 0.

A (input/output) REAL array, dimension (LDA, N)

On entry, the n-by-n matrix A 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, i.e.,

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 ow

erflow if we try 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

SGETC2(3)