redhat man page for dsptri

DSPTRI(l)								 )								 DSPTRI(l)

NAME
       DSPTRI - compute 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.  = '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.

LAPACK version 3.0						   15 June 2000 							 DSPTRI(l)