dsptri (l) - Linux Manuals

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

NAME

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

SYNOPSIS

SUBROUTINE DSPTRI(
UPLO, N, AP, IPIV, WORK, INFO )

    
CHARACTER UPLO

    
INTEGER INFO, N

    
INTEGER IPIV( * )

    
DOUBLE PRECISION AP( * ), WORK( * )

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.

ARGUMENTS

UPLO (input) CHARACTER*1
Specifies whether the details of the factorization are stored as an upper or lower triangular matrix. = aqUaq: Upper triangular, form is A = U*D*U**T;
= aqLaq: 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 = aqUaq, AP(i + (j-1)*j/2) = inv(A)(i,j) for 1<=i<=j; if UPLO = aqLaq, 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.

Pages related to dsptri

  • dsptri (3)
  • dsptrd (l) - reduces a real symmetric matrix A stored in packed form to symmetric tridiagonal form T by an orthogonal similarity transformation
  • dsptrf (l) - computes the factorization of a real symmetric matrix A stored in packed format using the Bunch-Kaufman diagonal pivoting method
  • dsptrs (l) - solves a system of linear equations A*X = B with a real symmetric matrix A stored in packed format using the factorization A = U*D*U**T or A = L*D*L**T computed by DSPTRF
  • dspcon (l) - estimates the reciprocal of the condition number (in the 1-norm) of a real symmetric packed matrix A using the factorization A = U*D*U**T or A = L*D*L**T computed by DSPTRF
  • dspev (l) - computes all the eigenvalues and, optionally, eigenvectors of a real symmetric matrix A in packed storage
  • dspevd (l) - computes all the eigenvalues and, optionally, eigenvectors of a real symmetric matrix A in packed storage
  • dspevx (l) - computes selected eigenvalues and, optionally, eigenvectors of a real symmetric matrix A in packed storage