Contents


NAME

     zgetf2 - compute an LU factorization  of  a  general  m-by-n
     matrix A using partial pivoting with row interchanges

SYNOPSIS

     SUBROUTINE ZGETF2(M, N, A, LDA, IPIV, INFO)

     DOUBLE COMPLEX A(LDA,*)
     INTEGER M, N, LDA, INFO
     INTEGER IPIV(*)

     SUBROUTINE ZGETF2_64(M, N, A, LDA, IPIV, INFO)

     DOUBLE COMPLEX A(LDA,*)
     INTEGER*8 M, N, LDA, INFO
     INTEGER*8 IPIV(*)

  F95 INTERFACE
     SUBROUTINE GETF2([M], [N], A, [LDA], IPIV, [INFO])

     COMPLEX(8), DIMENSION(:,:) :: A
     INTEGER :: M, N, LDA, INFO
     INTEGER, DIMENSION(:) :: IPIV

     SUBROUTINE GETF2_64([M], [N], A, [LDA], IPIV, [INFO])

     COMPLEX(8), DIMENSION(:,:) :: A
     INTEGER(8) :: M, N, LDA, INFO
     INTEGER(8), DIMENSION(:) :: IPIV

  C INTERFACE
     #include <sunperf.h>

     void zgetf2(int m, int n, doublecomplex  *a,  int  lda,  int
               *ipiv, int *info);

     void zgetf2_64(long m, long n, doublecomplex *a,  long  lda,
               long *ipiv, long *info);

PURPOSE

     zgetf2 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  algo-
     rithm.

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  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
               if it is used to solve a system of equations.