cgetrf(3S)

NAME
     CGETRF - compute an LU factorization of a general M-by-N matrix A using
     partial pivoting with row interchanges

SYNOPSIS
     SUBROUTINE CGETRF( M, N, A, LDA, IPIV, INFO )

         INTEGER        INFO, LDA, M, N

         INTEGER        IPIV( * )

         COMPLEX        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
     CGETRF computes an LU factorization of a general M-by-N matrix A using
     partial pivoting with row interchanges. The factorization has the form
        A = P * L * U
     where P is a permutation matrix, L is lower triangular with unit diagonal
     elements (lower trapezoidal if m > n), and U is upper triangular (upper
     trapezoidal if m < n).

     This is the right-looking Level 3 BLAS version of the algorithm.


ARGUMENTS
     M       (input) INTEGER
             The number of rows of the matrix A.  M >= 0.

     N       (input) INTEGER
             The number of columns of the matrix A.  N >= 0.

     A       (input/output) COMPLEX array, dimension (LDA,N)
             On entry, the M-by-N matrix to be factored.  On exit, the factors
             L and U from the factorization A = P*L*U; the unit diagonal
             elements of L are not stored.

     LDA     (input) INTEGER
             The leading dimension of the array A.  LDA >= max(1,M).
     IPIV    (output) INTEGER array, dimension (min(M,N))
             The pivot indices; for 1 <= i <= min(M,N), row i of the matrix
             was interchanged with row IPIV(i).

     INFO    (output) INTEGER
             = 0:  successful exit
             < 0:  if INFO = -i, the i-th argument had an illegal value
             > 0:  if INFO = i, U(i,i) is exactly zero. The factorization has
             been completed, but the factor U is exactly singular, and
             division by zero will occur if it is used to solve a system of
             equations.

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

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