dptrfs.f(3)							      LAPACK							       dptrfs.f(3)

NAME

       dptrfs.f -

SYNOPSIS

   Functions/Subroutines
       subroutine dptrfs (N, NRHS, D, E, DF, EF, B, LDB, X, LDX, FERR, BERR, WORK, INFO)
	   DPTRFS

Function/Subroutine Documentation
   subroutine dptrfs (integerN, integerNRHS, double precision, dimension( * )D, double precision, dimension( * )E, double precision, dimension( *
       )DF, double precision, dimension( * )EF, double precision, dimension( ldb, * )B, integerLDB, double precision, dimension( ldx, * )X,
       integerLDX, double precision, dimension( * )FERR, double precision, dimension( * )BERR, double precision, dimension( * )WORK, integerINFO)
       DPTRFS

       Purpose:

	    DPTRFS improves the computed solution to a system of linear
	    equations when the coefficient matrix is symmetric positive definite
	    and tridiagonal, and provides error bounds and backward error
	    estimates for the solution.

       Parameters:
	   N

		     N is INTEGER
		     The order of the matrix A.  N >= 0.

	   NRHS

		     NRHS is INTEGER
		     The number of right hand sides, i.e., the number of columns
		     of the matrix B.  NRHS >= 0.

	   D

		     D is DOUBLE PRECISION array, dimension (N)
		     The n diagonal elements of the tridiagonal matrix A.

	   E

		     E is DOUBLE PRECISION array, dimension (N-1)
		     The (n-1) subdiagonal elements of the tridiagonal matrix A.

	   DF

		     DF is DOUBLE PRECISION array, dimension (N)
		     The n diagonal elements of the diagonal matrix D from the
		     factorization computed by DPTTRF.

	   EF

		     EF is DOUBLE PRECISION array, dimension (N-1)
		     The (n-1) subdiagonal elements of the unit bidiagonal factor
		     L from the factorization computed by DPTTRF.

	   B

		     B is DOUBLE PRECISION array, dimension (LDB,NRHS)
		     The right hand side matrix B.

	   LDB

		     LDB is INTEGER
		     The leading dimension of the array B.  LDB >= max(1,N).

	   X

		     X is DOUBLE PRECISION array, dimension (LDX,NRHS)
		     On entry, the solution matrix X, as computed by DPTTRS.
		     On exit, the improved solution matrix X.

	   LDX

		     LDX is INTEGER
		     The leading dimension of the array X.  LDX >= max(1,N).

	   FERR

		     FERR is DOUBLE PRECISION array, dimension (NRHS)
		     The forward error bound for each solution vector
		     X(j) (the j-th column of the solution matrix X).
		     If XTRUE is the true solution corresponding to X(j), FERR(j)
		     is an estimated upper bound for the magnitude of the largest
		     element in (X(j) - XTRUE) divided by the magnitude of the
		     largest element in X(j).

	   BERR

		     BERR is DOUBLE PRECISION array, dimension (NRHS)
		     The componentwise relative backward error of each solution
		     vector X(j) (i.e., the smallest relative change in
		     any element of A or B that makes X(j) an exact solution).

	   WORK

		     WORK is DOUBLE PRECISION array, dimension (2*N)

	   INFO

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

       Internal Parameters:

	     ITMAX is the maximum number of steps of iterative refinement.

       Author:
	   Univ. of Tennessee

	   Univ. of California Berkeley

	   Univ. of Colorado Denver

	   NAG Ltd.

       Date:
	   November 2011

       Definition at line 163 of file dptrfs.f.

Author
       Generated automatically by Doxygen for LAPACK from the source code.

Version 3.4.1							  Sun May 26 2013						       dptrfs.f(3)