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RedHat 9 (Linux i386) - man page for dgetri (redhat section l)

DGETRI(l)					)					DGETRI(l)

NAME
       DGETRI - compute the inverse of a matrix using the LU factorization computed by DGETRF

SYNOPSIS
       SUBROUTINE DGETRI( N, A, LDA, IPIV, WORK, LWORK, INFO )

	   INTEGER	  INFO, LDA, LWORK, N

	   INTEGER	  IPIV( * )

	   DOUBLE	  PRECISION A( LDA, * ), WORK( * )

PURPOSE
       DGETRI  computes  the  inverse  of a matrix using the LU factorization computed by DGETRF.
       This method inverts U and then computes inv(A) by solving the system inv(A)*L = inv(U) for
       inv(A).

ARGUMENTS
       N       (input) INTEGER
	       The order of the matrix A.  N >= 0.

       A       (input/output) DOUBLE PRECISION array, dimension (LDA,N)
	       On  entry,  the	factors  L  and U from the factorization A = P*L*U as computed by
	       DGETRF.	On exit, if INFO = 0, the inverse of the original matrix A.

       LDA     (input) INTEGER
	       The leading dimension of the array A.  LDA >= max(1,N).

       IPIV    (input) INTEGER array, dimension (N)
	       The pivot indices from DGETRF; for 1<=i<=N, row i of the matrix	was  interchanged
	       with row IPIV(i).

       WORK    (workspace/output) DOUBLE PRECISION array, dimension (LWORK)
	       On exit, if INFO=0, then WORK(1) returns the optimal LWORK.

       LWORK   (input) INTEGER
	       The  dimension  of  the	array  WORK.  LWORK >= max(1,N).  For optimal performance
	       LWORK >= N*NB, where NB is the optimal blocksize returned by ILAENV.

	       If LWORK = -1, then a workspace query is assumed; the routine only calculates  the
	       optimal	size of the WORK array, returns this value as the first entry of the WORK
	       array, and no error message related to LWORK is issued by XERBLA.

       INFO    (output) INTEGER
	       = 0:  successful exit
	       < 0:  if INFO = -i, the i-th argument had an illegal value
	       > 0:  if INFO = i, U(i,i) is exactly zero; the matrix is singular and its  inverse
	       could not be computed.

LAPACK version 3.0			   15 June 2000 				DGETRI(l)


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