DGETRI(3F)DGETRI(3F)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( LWORK )
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.
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.
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