Contents
dsttrs - computes the solution to a real system of linear
equations A * X = B
SUBROUTINE DSTTRS(N, NRHS, L, D, SUBL, B, LDB, IPIV, INFO)
INTEGER N, NRHS, LDB, INFO
INTEGER IPIV(*)
DOUBLE PRECISION L(*), D(*), SUBL(*), B(LDB,*)
SUBROUTINE DSTTRS_64(N, NRHS, L, D, SUBL, B, LDB, IPIV, INFO)
INTEGER*8 N, NRHS, LDB, INFO
INTEGER*8 IPIV(*)
DOUBLE PRECISION L(*), D(*), SUBL(*), B(LDB,*)
F95 INTERFACE
SUBROUTINE STTRS([N], [NRHS], L, D, SUBL, B, [LDB], IPIV, [INFO])
INTEGER :: N, NRHS, LDB, INFO
INTEGER, DIMENSION(:) :: IPIV
REAL(8), DIMENSION(:) :: L, D, SUBL
REAL(8), DIMENSION(:,:) :: B
SUBROUTINE STTRS_64([N], [NRHS], L, D, SUBL, B, [LDB], IPIV, [INFO])
INTEGER(8) :: N, NRHS, LDB, INFO
INTEGER(8), DIMENSION(:) :: IPIV
REAL(8), DIMENSION(:) :: L, D, SUBL
REAL(8), DIMENSION(:,:) :: B
C INTERFACE
#include <sunperf.h>
void dsttrs(int n, int nrhs, double *l, double *d, double
*subl, double *b, int ldb, int *ipiv, int *info);
void dsttrs_64(long n, long nrhs, double *l, double *d, dou-
ble *subl, double *b, long ldb, long *ipiv, long
*info);
dsttrs computes the solution to a real system of linear
equations A * X = B, where A is an N-by-N symmetric tridiag-
onal matrix and X and B are N-by-NRHS matrices.
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.
L (input) REAL array, dimension (N-1)
On entry, the subdiagonal elements of L.
D (input) REAL array, dimension (N)
On entry, the diagonal elements of D.
SUBL (input)
REAL array, dimension (N-2)
On entry, the second subdiagonal elements of L.
B (input/output)
REAL array, dimension
(LDB, NRHS) On entry, the N-by-NRHS right hand
side matrix B. On exit, if INFO = 0, the N-by-
NRHS solution matrix X.
LDB (input)
INTEGER
The leading dimension of the array B. LDB >=
max(1, N)
IPIV (output)
INTEGER array, dimension (N)
Details of the interchanges and block pivot. If
IPIV(K) > 0, 1 by 1 pivot, and if IPIV(K) = K + 1
an interchange done; If IPIV(K) < 0, 2 by 2
pivot, no interchange required.
INFO (output)
INTEGER
= 0: successful exit
< 0: if INFO = -k, the k-th argument had an ille-
gal value