dgtsv(3P) Sun Performance Library dgtsv(3P)NAMEdgtsv - solve the equation A*X = B,
SYNOPSIS
SUBROUTINE DGTSV(N, NRHS, LOW, D, UP, B, LDB, INFO)
INTEGER N, NRHS, LDB, INFO
DOUBLE PRECISION LOW(*), D(*), UP(*), B(LDB,*)
SUBROUTINE DGTSV_64(N, NRHS, LOW, D, UP, B, LDB, INFO)
INTEGER*8 N, NRHS, LDB, INFO
DOUBLE PRECISION LOW(*), D(*), UP(*), B(LDB,*)
F95 INTERFACE
SUBROUTINE GTSV([N], [NRHS], LOW, D, UP, B, [LDB], [INFO])
INTEGER :: N, NRHS, LDB, INFO
REAL(8), DIMENSION(:) :: LOW, D, UP
REAL(8), DIMENSION(:,:) :: B
SUBROUTINE GTSV_64([N], [NRHS], LOW, D, UP, B, [LDB], [INFO])
INTEGER(8) :: N, NRHS, LDB, INFO
REAL(8), DIMENSION(:) :: LOW, D, UP
REAL(8), DIMENSION(:,:) :: B
C INTERFACE
#include <sunperf.h>
void dgtsv(int n, int nrhs, double *low, double *d, double *up, double
*b, int ldb, int *info);
void dgtsv_64(long n, long nrhs, double *low, double *d, double *up,
double *b, long ldb, long *info);
PURPOSEdgtsv solves the equation
where A is an n by n tridiagonal matrix, by Gaussian elimination with
partial pivoting.
Note that the equation A'*X = B may be solved by interchanging the
order of the arguments DU and DL.
ARGUMENTS
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/output)
On entry, LOW must contain the (n-1) sub-diagonal elements of
A.
On exit, LOW is overwritten by the (n-2) elements of the sec‐
ond super-diagonal of the upper triangular matrix U from the
LU factorization of A, in LOW(1), ..., LOW(n-2).
D (input/output)
On entry, D must contain the diagonal elements of A.
On exit, D is overwritten by the n diagonal elements of U.
UP (input/output)
On entry, UP must contain the (n-1) super-diagonal elements
of A.
On exit, UP is overwritten by the (n-1) elements of the first
super-diagonal of U.
B (input/output)
On entry, the N by NRHS matrix of right hand side matrix B.
On exit, if INFO = 0, the N by NRHS solution matrix X.
LDB (input)
The leading dimension of the array B. LDB >= max(1,N).
INFO (output)
= 0: successful exit
< 0: if INFO = -i, the i-th argument had an illegal value
> 0: if INFO = i, U(i,i) is exactly zero, and the solution
has not been computed. The factorization has not been com‐
pleted unless i = N.
6 Mar 2009 dgtsv(3P)
