Home Man
Search
Today's Posts
Register

Linux & Unix Commands - Search Man Pages

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

SPTRFS(l)					)					SPTRFS(l)

NAME
       SPTRFS  -  improve  the computed solution to a system of linear equations when the coeffi-
       cient matrix is symmetric positive definite and tridiagonal, and provides error bounds and
       backward error estimates for the solution

SYNOPSIS
       SUBROUTINE SPTRFS( N, NRHS, D, E, DF, EF, B, LDB, X, LDX, FERR, BERR, WORK, INFO )

	   INTEGER	  INFO, LDB, LDX, N, NRHS

	   REAL 	  B(  LDB,  *  ), BERR( * ), D( * ), DF( * ), E( * ), EF( * ), FERR( * ),
			  WORK( * ), X( LDX, * )

PURPOSE
       SPTRFS 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 back-
       ward error estimates for the solution.

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

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

       D       (input) REAL array, dimension (N)
	       The n diagonal elements of the tridiagonal matrix A.

       E       (input) REAL array, dimension (N-1)
	       The (n-1) subdiagonal elements of the tridiagonal matrix A.

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

       EF      (input) REAL array, dimension (N-1)
	       The (n-1) subdiagonal elements of the unit bidiagonal factor L from the factoriza-
	       tion computed by SPTTRF.

       B       (input) REAL array, dimension (LDB,NRHS)
	       The right hand side matrix B.

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

       X       (input/output) REAL array, dimension (LDX,NRHS)
	       On  entry,  the	solution  matrix X, as computed by SPTTRS.  On exit, the improved
	       solution matrix X.

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

       FERR    (output) REAL 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    (output) REAL 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  solu-
	       tion).

       WORK    (workspace) REAL array, dimension (2*N)

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

PARAMETERS
       ITMAX is the maximum number of steps of iterative refinement.

LAPACK version 3.0			   15 June 2000 				SPTRFS(l)


All times are GMT -4. The time now is 07:27 AM.

Unix & Linux Forums Content Copyrightę1993-2018. All Rights Reserved.
UNIX.COM Login
Username:
Password:  
Show Password