Contents

• NAME
• SYNOPSIS
  • F95 INTERFACE
  • C INTERFACE
• PURPOSE
• ARGUMENTS

NAME

     dstsv - compute the solution to a system of linear equations
     A * X = B where A is a symmetric tridiagonal matrix

SYNOPSIS

     SUBROUTINE DSTSV(N, NRHS, L, D, SUBL, B, LDB, IPIV, INFO)

     INTEGER N, NRHS, LDB, INFO
     INTEGER IPIV(*)
     DOUBLE PRECISION L(*), D(*), SUBL(*), B(LDB,*)

     SUBROUTINE DSTSV_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 STSV([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 STSV_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 dstsv(int n, int nrhs, double  *l,  double  *d,  double
               *subl, double *b, int ldb, int *ipiv, int *info);

     void dstsv_64(long n, long nrhs, double *l, double *d,  dou-
               ble  *subl,  double *b, long ldb, long *ipiv, long
               *info);

PURPOSE

     dstsv computes the solution to a system of linear  equations
     A * X = B where A is a symmetric tridiagonal matrix.

ARGUMENTS

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

     NRHS (input)
               The number of right hand sides in B.

     L (input/output)
                REAL array, dimension (N-1)
               On entry, the n-1 subdiagonal elements of the tri-
               diagonal  matrix A.  On exit, part of the factori-
               zation of A.

     D (input/output)
                REAL array, dimension (N)
               On entry, the n diagonal elements of the tridiago-
               nal matrix A.  On exit, the n diagonal elements of
               the diagonal matrix D from the factorization of A.

     SUBL (output)
                REAL array, dimension (N-2)
               On exit, part of the factorization of A.

     B (input/output)
               The columns of B contain the right hand sides.

     LDB (input)
               The leading dimension of B as specified in a  type
               or DIMENSION statement.

     IPIV (output)
                INTEGER array, dimension (N)
               On exit, the pivot indices of the factorization.

     INFO (output)
                INTEGER
               = 0:  successful exit
               < 0:  if INFO = -i, the i-th argument had an ille-
               gal value
               > 0:  if INFO = i, D(k,k) is  exactly  zero.   The
               factorization  has  been  completed, but the block
               diagonal matrix D is exactly singular and division
               by zero will occur if it is used to solve a system
               of equations.