DSPTRI
Purpose
DSPTRI computes the inverse of a real symmetric indefinite matrix
A in packed storage using the factorization A = U*D*U**T or
A = L*D*L**T computed by DSPTRF.
A in packed storage using the factorization A = U*D*U**T or
A = L*D*L**T computed by DSPTRF.
Arguments
| UPLO |
(input) CHARACTER*1
Specifies whether the details of the factorization are stored
as an upper or lower triangular matrix. = 'U': Upper triangular, form is A = U*D*U**T; = 'L': Lower triangular, form is A = L*D*L**T. |
| N |
(input) INTEGER
The order of the matrix A. N >= 0.
|
| AP |
(input/output) DOUBLE PRECISION array, dimension (N*(N+1)/2)
On entry, the block diagonal matrix D and the multipliers
used to obtain the factor U or L as computed by DSPTRF, stored as a packed triangular matrix. On exit, if INFO = 0, the (symmetric) inverse of the original matrix, stored as a packed triangular matrix. The j-th column of inv(A) is stored in the array AP as follows: if UPLO = 'U', AP(i + (j-1)*j/2) = inv(A)(i,j) for 1<=i<=j; if UPLO = 'L', AP(i + (j-1)*(2n-j)/2) = inv(A)(i,j) for j<=i<=n. |
| IPIV |
(input) INTEGER array, dimension (N)
Details of the interchanges and the block structure of D
as determined by DSPTRF. |
| WORK |
(workspace) DOUBLE PRECISION array, dimension (N)
|
| INFO |
(output) INTEGER
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value > 0: if INFO = i, D(i,i) = 0; the matrix is singular and its inverse could not be computed. |