DGETF2(3f)

NAME
DGETF2 - an LU factorization of a general m-by-n matrix A using partial pivoting with row interchanges

SYNOPSIS

SUBROUTINE DGETF2(
    M, N, A, LDA, IPIV, INFO )

INTEGER
    INFO, LDA, M, N

INTEGER
    IPIV( * )

DOUBLE
    PRECISION A( LDA, * )

PURPOSE
DGETF2 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 2 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) DOUBLE PRECISION 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 = -k, the k-th argument had an illegal value
    > 0: if INFO = k, U(k,k) 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.