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

NAME

dptts2 - solve a tridiagonal system of the form A * X = B using the L*D*L' factorization of A computed by SPTTRF

SYNOPSIS

  SUBROUTINE DPTTS2( N, NRHS, D, E, B, LDB)
  INTEGER N, NRHS, LDB
  DOUBLE PRECISION D(*), E(*), B(LDB,*)

  SUBROUTINE DPTTS2_64( N, NRHS, D, E, B, LDB)
  INTEGER*8 N, NRHS, LDB
  DOUBLE PRECISION D(*), E(*), B(LDB,*)

F95 INTERFACE

  SUBROUTINE DPTTS2( N, NRHS, D, E, B, LDB)
  INTEGER :: N, NRHS, LDB
  REAL(8), DIMENSION(:) :: D, E
  REAL(8), DIMENSION(:,:) :: B

  SUBROUTINE DPTTS2_64( N, NRHS, D, E, B, LDB)
  INTEGER(8) :: N, NRHS, LDB
  REAL(8), DIMENSION(:) :: D, E
  REAL(8), DIMENSION(:,:) :: B

C INTERFACE

#include <sunperf.h>

void dptts2(int n, int nrhs, double *d, double *e, double *b, int ldb);

void dptts2_64(long n, long nrhs, double *d, double *e, double *b, long ldb);

PURPOSE

dptts2 solves a tridiagonal system of the form A * X = B using the L*D*L' factorization of A computed by SPTTRF. D is a diagonal matrix specified in the vector D, L is a unit bidiagonal matrix whose subdiagonal is specified in the vector E, and X and B are N by NRHS matrices.

ARGUMENTS

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

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

• D (input)
  The n diagonal elements of the diagonal matrix D from the L*D*L' factorization of A.

• E (input)
  The (n-1) subdiagonal elements of the unit bidiagonal factor L from the L*D*L' factorization of A. E can also be regarded as the superdiagonal of the unit bidiagonal factor U from the factorization A = U'*D*U.

• B (input/output)
  On entry, the right hand side vectors B for the system of linear equations. On exit, the solution vectors, X.

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