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( LWORK )

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.

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.

SunSoft, Inc.  —  Last change: 27 Jun 1995