
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 ith 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) 
