dgetrf (l)  Linux Manuals
dgetrf: computes an LU factorization of a general MbyN matrix A using partial pivoting with row interchanges
NAME
DGETRF  computes an LU factorization of a general MbyN matrix A using partial pivoting with row interchangesSYNOPSIS
 SUBROUTINE DGETRF(
 M, N, A, LDA, IPIV, INFO )
 INTEGER INFO, LDA, M, N
 INTEGER IPIV( * )
 DOUBLE PRECISION A( LDA, * )
PURPOSE
DGETRF computes an LU factorization of a general MbyN matrix A using partial pivoting with row interchanges. The factorization has the formA
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 rightlooking 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) DOUBLE PRECISION array, dimension (LDA,N)
 On entry, the MbyN 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 ith 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.