redhat man page for sgetri

SGETRI(l)								 )								 SGETRI(l)

NAME
       SGETRI - compute the inverse of a matrix using the LU factorization computed by SGETRF

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

	   INTEGER	  INFO, LDA, LWORK, N

	   INTEGER	  IPIV( * )

	   REAL 	  A( LDA, * ), WORK( * )

PURPOSE
       SGETRI  computes  the inverse of a matrix using the LU factorization computed by SGETRF.  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) REAL array, dimension (LDA,N)
	       On entry, the factors L and U from the factorization A = P*L*U as computed by SGETRF.  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 SGETRF; for 1<=i<=N, row i of the matrix was interchanged with row IPIV(i).

       WORK    (workspace/output) REAL 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 							 SGETRI(l)