DGETC2(3S)DGETC2(3S)NAME
DGETC2 - compute an LU factorization with complete pivoting of the n-by-n
matrix A
SYNOPSIS
SUBROUTINE DGETC2( N, A, LDA, IPIV, JPIV, INFO )
INTEGER INFO, LDA, N
INTEGER IPIV( * ), JPIV( * )
DOUBLE PRECISION A( LDA, * )
IMPLEMENTATION
These routines are part of the SCSL Scientific Library and can be loaded
using either the -lscs or the -lscs_mp option. The -lscs_mp option
directs the linker to use the multi-processor version of the library.
When linking to SCSL with -lscs or -lscs_mp, the default integer size is
4 bytes (32 bits). Another version of SCSL is available in which integers
are 8 bytes (64 bits). This version allows the user access to larger
memory sizes and helps when porting legacy Cray codes. It can be loaded
by using the -lscs_i8 option or the -lscs_i8_mp option. A program may use
only one of the two versions; 4-byte integer and 8-byte integer library
calls cannot be mixed.
PURPOSE
DGETC2 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 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 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).
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DGETC2(3S)DGETC2(3S)
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 by
Bo Kagstrom and Peter Poromaa, Department of Computing Science,
Umea University, S-901 87 Umea, Sweden.
SEE ALSOINTRO_LAPACK(3S), INTRO_SCSL(3S)
This man page is available only online.
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