dgtrfs man page on OpenIndiana

Man page or keyword search:  
man Server   20441 pages
apropos Keyword Search (all sections)
Output format
OpenIndiana logo
[printable version]

dgtrfs(3P)		    Sun Performance Library		    dgtrfs(3P)

NAME
       dgtrfs  - improve the computed solution to a system of linear equations
       when the coefficient matrix is tridiagonal, and provides	 error	bounds
       and backward error estimates for the solution

SYNOPSIS
       SUBROUTINE DGTRFS(TRANSA, N, NRHS, LOW, D, UP, LOWF, DF, UPF1,
	     UPF2, IPIVOT, B, LDB, X, LDX, FERR, BERR, WORK, WORK2, INFO)

       CHARACTER * 1 TRANSA
       INTEGER N, NRHS, LDB, LDX, INFO
       INTEGER IPIVOT(*), WORK2(*)
       DOUBLE PRECISION LOW(*), D(*), UP(*), LOWF(*), DF(*), UPF1(*), UPF2(*),
       B(LDB,*), X(LDX,*), FERR(*), BERR(*), WORK(*)

       SUBROUTINE DGTRFS_64(TRANSA, N, NRHS, LOW, D, UP, LOWF, DF,
	     UPF1, UPF2, IPIVOT, B, LDB, X, LDX, FERR, BERR, WORK, WORK2,
	     INFO)

       CHARACTER * 1 TRANSA
       INTEGER*8 N, NRHS, LDB, LDX, INFO
       INTEGER*8 IPIVOT(*), WORK2(*)
       DOUBLE PRECISION LOW(*), D(*), UP(*), LOWF(*), DF(*), UPF1(*), UPF2(*),
       B(LDB,*), X(LDX,*), FERR(*), BERR(*), WORK(*)

   F95 INTERFACE
       SUBROUTINE GTRFS([TRANSA], [N], [NRHS], LOW, D, UP, LOWF, DF,
	      UPF1, UPF2, IPIVOT, B, [LDB], X, [LDX], FERR, BERR, [WORK],
	      [WORK2], [INFO])

       CHARACTER(LEN=1) :: TRANSA
       INTEGER :: N, NRHS, LDB, LDX, INFO
       INTEGER, DIMENSION(:) :: IPIVOT, WORK2
       REAL(8),	 DIMENSION(:) :: LOW, D, UP, LOWF, DF, UPF1, UPF2, FERR, BERR,
       WORK
       REAL(8), DIMENSION(:,:) :: B, X

       SUBROUTINE GTRFS_64([TRANSA], [N], [NRHS], LOW, D, UP, LOWF,
	      DF, UPF1, UPF2, IPIVOT, B, [LDB], X, [LDX], FERR, BERR, [WORK],
	      [WORK2], [INFO])

       CHARACTER(LEN=1) :: TRANSA
       INTEGER(8) :: N, NRHS, LDB, LDX, INFO
       INTEGER(8), DIMENSION(:) :: IPIVOT, WORK2
       REAL(8), DIMENSION(:) :: LOW, D, UP, LOWF, DF, UPF1, UPF2, FERR,	 BERR,
       WORK
       REAL(8), DIMENSION(:,:) :: B, X

   C INTERFACE
       #include <sunperf.h>

       void  dgtrfs(char transa, int n, int nrhs, double *low, double *d, dou‐
		 ble *up, double  *lowf,  double  *df,	double	*upf1,	double
		 *upf2,	 int  *ipivot, double *b, int ldb, double *x, int ldx,
		 double *ferr, double *berr, int *info);

       void dgtrfs_64(char transa, long n, long nrhs, double *low, double  *d,
		 double	 *up,  double  *lowf, double *df, double *upf1, double
		 *upf2, long *ipivot, double *b, long  ldb,  double  *x,  long
		 ldx, double *ferr, double *berr, long *info);

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

ARGUMENTS
       TRANSA (input)
		 Specifies the form of the system of equations:
		 = 'N':	 A * X = B     (No transpose)
		 = 'T':	 A**T * X = B  (Transpose)
		 = 'C':	 A**H * X = B  (Conjugate transpose = Transpose)

		 TRANSA is defaulted to 'N' for F95 INTERFACE.

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

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

       LOW (input)
		 The (n-1) subdiagonal elements of A.

       D (input) The diagonal elements of A.

       UP (input)
		 The (n-1) superdiagonal elements of A.

       LOWF (input)
		 The (n-1) multipliers that define the matrix L	 from  the  LU
		 factorization of A as computed by DGTTRF.

       DF (input)
		 The n diagonal elements of the upper triangular matrix U from
		 the LU factorization of A.

       UPF1 (input)
		 The (n-1) elements of the first superdiagonal of U.

       UPF2 (input)
		 The (n-2) elements of the second superdiagonal of U.

       IPIVOT (input)
		 The pivot indices; for 1 <= i <= n, row i of the  matrix  was
		 interchanged  with  row  IPIVOT(i).  IPIVOT(i) will always be
		 either i or i+1; IPIVOT(i) = i indicates  a  row  interchange
		 was not required.

       B (input) The right hand side matrix B.

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

       X (input/output)
		 On  entry,  the solution matrix X, as computed by DGTTRS.  On
		 exit, the improved solution matrix X.

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

       FERR (output)
		 The estimated 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	 esti‐
		 mated upper bound for the magnitude of the largest element in
		 (X(j) - XTRUE) divided by the magnitude of the	 largest  ele‐
		 ment  in  X(j).   The estimate is as reliable as the estimate
		 for RCOND, and is almost always a slight overestimate of  the
		 true error.

       BERR (output)
		 The  componentwise  relative  backward error of each solution
		 vector X(j) (i.e., the smallest relative change in  any  ele‐
		 ment of A or B that makes X(j) an exact solution).

       WORK (workspace)
		 dimension(3*N)

       WORK2 (workspace)
		 dimension(N)

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

				  6 Mar 2009			    dgtrfs(3P)
[top]

List of man pages available for OpenIndiana

Copyright (c) for man pages and the logo by the respective OS vendor.

For those who want to learn more, the polarhome community provides shell access and support.

[legal] [privacy] [GNU] [policy] [cookies] [netiquette] [sponsors] [FAQ]
Tweet
Polarhome, production since 1999.
Member of Polarhome portal.
Based on Fawad Halim's script.
....................................................................
Vote for polarhome
Free Shell Accounts :: the biggest list on the net