


DPTTS2(3f)         LAPACK routine (version 3.1)        DPTTS2(3f)


NAME
       DPTTS2  -  a tridiagonal system of the form  A * X = B using the L*D*L'
       factorization of A computed by DPTTRF

SYNOPSIS
       SUBROUTINE DPTTS2( N, NRHS, D, E, B, LDB )

           INTEGER        LDB, N, NRHS

           DOUBLE         PRECISION B( LDB, * ), D( * ), E( * )

PURPOSE
       DPTTS2 solves a tridiagonal system of the form
          A * X = B using the L*D*L' factorization of A computed by DPTTRF.  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) INTEGER
               The order of the tridiagonal 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.

       D       (input) DOUBLE PRECISION array, dimension (N)
               The n diagonal elements of  the  diagonal  matrix  D  from  the
               L*D*L' factorization of A.

       E       (input) DOUBLE PRECISION array, dimension (N-1)
               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 fac-
               torization A = U'*D*U.

       B       (input/output) DOUBLE PRECISION array, dimension (LDB,NRHS)
               On entry, the right hand side vectors B for the system of  lin-
               ear equations.  On exit, the solution vectors, X.

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














 LAPACK routine (version 3November 2006                         1


