zgetc2(3S)

NAME
     ZGETC2 - compute an LU factorization, using complete pivoting, 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, * )

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
     ZGETC2 computes an LU factorization, using 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 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.


SEE ALSO
     INTRO_LAPACK(3S), INTRO_SCSL(3S)

     This man page is available only online.