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RedHat 9 (Linux i386) - man page for dsptri (redhat section l)

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  fac-
	       tor 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)


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