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

SPTCON(l)					)					SPTCON(l)

NAME
       SPTCON  - compute the reciprocal of the condition number (in the 1-norm) of a real symmet-
       ric positive definite tridiagonal matrix using the factorization  A  =  L*D*L**T  or  A	=
       U**T*D*U computed by SPTTRF

SYNOPSIS
       SUBROUTINE SPTCON( N, D, E, ANORM, RCOND, WORK, INFO )

	   INTEGER	  INFO, N

	   REAL 	  ANORM, RCOND

	   REAL 	  D( * ), E( * ), WORK( * )

PURPOSE
       SPTCON computes the reciprocal of the condition number (in the 1-norm) of a real symmetric
       positive definite tridiagonal matrix using the factorization A = L*D*L**T or A =  U**T*D*U
       computed  by  SPTTRF.   Norm(inv(A)) is computed by a direct method, and the reciprocal of
       the condition number is computed as
		    RCOND = 1 / (ANORM * norm(inv(A))).

ARGUMENTS
       N       (input) INTEGER
	       The order of the matrix A.  N >= 0.

       D       (input) REAL array, dimension (N)
	       The n diagonal elements of the diagonal matrix D from the factorization of  A,  as
	       computed by SPTTRF.

       E       (input) REAL array, dimension (N-1)
	       The (n-1) off-diagonal elements of the unit bidiagonal factor U or L from the fac-
	       torization of A,  as computed by SPTTRF.

       ANORM   (input) REAL
	       The 1-norm of the original matrix A.

       RCOND   (output) REAL
	       The reciprocal of the condition number of  the  matrix  A,  computed  as  RCOND	=
	       1/(ANORM * AINVNM), where AINVNM is the 1-norm of inv(A) computed in this routine.

       WORK    (workspace) REAL array, dimension (N)

       INFO    (output) INTEGER
	       = 0:  successful exit
	       < 0:  if INFO = -i, the i-th argument had an illegal value

FURTHER DETAILS
       The  method  used  is described in Nicholas J. Higham, "Efficient Algorithms for Computing
       the Condition Number of a Tridiagonal Matrix", SIAM J. Sci. Stat. Comput., Vol. 7, No.  1,
       January 1986.

LAPACK version 3.0			   15 June 2000 				SPTCON(l)


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