-
template<typename T>
void sptri(char *uplo, integer *n, T *ap, integer *ipiv, T *work, integer *info)# SPTRI computes the inverse of a real symmetric indefinite matrix A.
Purpose:
SPTRI 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 SPTRF.
- Parameters:
UPLO – [in]
UPLO is 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 – [in]
N is INTEGER
The order of the matrix A. N >= 0.
AP – [inout]
AP is REAL 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 SSPTRF, 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 – [in]
IPIV is INTEGER array, dimension (N)
Details of the interchanges and the block structure of D as determined by SPTRF.
WORK – [out] WORK is REAL array, dimension (N)
INFO – [out]
INFO is 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.