- SUBROUTINE DGETF2(
- M, N, A, LDA, IPIV, INFO )
- INTEGER INFO, LDA, M, N
- INTEGER IPIV( * )
- DOUBLE PRECISION A( LDA, * )
PURPOSEDGETF2 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.
- 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.