dgetc2 (l)  Linux Man Pages
dgetc2: computes an LU factorization with complete pivoting of the nbyn matrix A
NAME
DGETC2  computes an LU factorization with complete pivoting of the nbyn matrix ASYNOPSIS
 SUBROUTINE DGETC2(
 N, A, LDA, IPIV, JPIV, INFO )
 INTEGER INFO, LDA, N
 INTEGER IPIV( * ), JPIV( * )
 DOUBLE PRECISION A( LDA, * )
PURPOSE
DGETC2 computes an LU factorization with complete pivoting of the nbyn 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 the Level 2 BLAS algorithm.
ARGUMENTS
 N (input) INTEGER
 The order of the matrix A. N >= 0.
 A (input/output) DOUBLE PRECISION array, dimension (LDA, N)
 On entry, the nbyn 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 owerflow if we try to solve for x in Ax = b. So U is perturbed to avoid the overflow.
FURTHER DETAILS
Based on contributions byBo Kagstrom and Peter Poromaa, Department of Computing Science,
Umea University, S901 87 Umea, Sweden.