SGETF2 - compute an LU factorization of a general m-by-n
matrix A using partial pivoting with row interchanges
SYNOPSIS
SUBROUTINE SGETF2( M, N, A, LDA, IPIV, INFO )
INTEGER INFO, LDA, M, N
INTEGER IPIV( * )
REAL A( LDA, * )
PURPOSE
SGETF2 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) REAL 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 ille
gal value
> 0: if INFO = k, U(k,k) is exactly zero. The fac
torization has been completed, but the factor U is
exactly singular, and division by zero will occur
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