• NAME
• SYNOPSIS
• F95 INTERFACE
• C INTERFACE
• PURPOSE
• ARGUMENTS

NAME

dgetf2 - compute 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 M, N, LDA, INFO
  INTEGER IPIV(*)
  DOUBLE PRECISION A(LDA,*)

  SUBROUTINE DGETF2_64( M, N, A, LDA, IPIV, INFO)
  INTEGER*8 M, N, LDA, INFO
  INTEGER*8 IPIV(*)
  DOUBLE PRECISION A(LDA,*)

F95 INTERFACE

  SUBROUTINE GETF2( [M], [N], A, [LDA], IPIV, [INFO])
  INTEGER :: M, N, LDA, INFO
  INTEGER, DIMENSION(:) :: IPIV
  REAL(8), DIMENSION(:,:) :: A

  SUBROUTINE GETF2_64( [M], [N], A, [LDA], IPIV, [INFO])
  INTEGER(8) :: M, N, LDA, INFO
  INTEGER(8), DIMENSION(:) :: IPIV
  REAL(8), DIMENSION(:,:) :: A

C INTERFACE

#include <sunperf.h>

void dgetf2(int m, int n, double *a, int lda, int *ipiv, int *info);

void dgetf2_64(long m, long n, double *a, long lda, long *ipiv, long *info);

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)
  The number of rows of the matrix A. M > = 0.

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

• A (input/output)
  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)
  The leading dimension of the array A. LDA > = max(1,M).

• IPIV (output)
  The pivot indices; for 1 < = i < = min(M,N), row i of the matrix was interchanged with row IPIV(i).

• INFO (output)
  

   = 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.