


ZPTTS2(3f)         LAPACK routine (version 3.1)        ZPTTS2(3f)


NAME
       ZPTTS2  - a tridiagonal system of the form  A * X = B using the factor-
       ization A = U'*D*U or A = L*D*L' computed by ZPTTRF

SYNOPSIS
       SUBROUTINE ZPTTS2( IUPLO, N, NRHS, D, E, B, LDB )

           INTEGER        IUPLO, LDB, N, NRHS

           DOUBLE         PRECISION D( * )

           COMPLEX*16     B( LDB, * ), E( * )

PURPOSE
       ZPTTS2 solves a tridiagonal system of the form
          A * X = B using the factorization A = U'*D*U or A = L*D*L'  computed
       by  ZPTTRF.  D is a diagonal matrix specified in the vector D, U (or L)
       is a unit bidiagonal matrix whose superdiagonal (subdiagonal) is speci-
       fied in the vector E, and X and B are N by NRHS matrices.


ARGUMENTS
       IUPLO   (input) INTEGER
               Specifies  the form of the factorization and whether the vector
               E is the superdiagonal of the upper bidiagonal factor U or  the
               subdiagonal  of  the  lower  bidiagonal  factor  L.   = 1:  A =
               U'*D*U, E is the superdiagonal of U
               = 0:  A = L*D*L', E is the subdiagonal of L

       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 fac-
               torization A = U'*D*U or A = L*D*L'.

       E       (input) COMPLEX*16 array, dimension (N-1)
               If IUPLO = 1, the (n-1)  superdiagonal  elements  of  the  unit
               bidiagonal  factor  U  from  the  factorization A = U'*D*U.  If
               IUPLO = 0, the (n-1) subdiagonal elements of the unit  bidiago-
               nal factor L from the factorization A = L*D*L'.

       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


