sgetri()

subroutine sgetri	(	integer	n,
		real, dimension( lda, * )	a,
		integer	lda,
		integer, dimension( * )	ipiv,
		real, dimension( * )	work,
		integer	lwork,
		integer	info )

SGETRI

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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).
!> 

Parameters

[in]	N	!> N is INTEGER !> The order of the matrix A. N >= 0. !>
[in,out]	A	!> A is 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. !>
[in]	LDA	!> LDA is INTEGER !> The leading dimension of the array A. LDA >= max(1,N). !>
[in]	IPIV	!> IPIV is INTEGER array, dimension (N) !> The pivot indices from SGETRF; for 1<=i<=N, row i of the !> matrix was interchanged with row IPIV(i). !>
[out]	WORK	!> WORK is REAL array, dimension (MAX(1,LWORK)) !> On exit, if INFO=0, then WORK(1) returns the optimal LWORK. !>
[in]	LWORK	!> LWORK is 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. !>
[out]	INFO	!> INFO is 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. !>

Author

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.