ZPTTRS(3)                  MathKeisan LAPACK routine                 ZPTTRS(3)



NAME
       ZPTTRS  - 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 ZPTTRS( UPLO, N, NRHS, D, E, B, LDB, INFO )

           CHARACTER      UPLO

           INTEGER        INFO, LDB, N, NRHS

           DOUBLE         PRECISION D( * )

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

PURPOSE
       ZPTTRS 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
       UPLO    (input) CHARACTER*1
               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.  = 'U':  A =
               U'*D*U, E is the superdiagonal of U
               = 'L':  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 UPLO = 'U', the (n-1) superdiagonal  elements  of  the  unit
               bidiagonal factor U from the factorization A = U'*D*U.  If UPLO
               = 'L', the (n-1) subdiagonal elements of  the  unit  bidiagonal
               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).

       INFO    (output) INTEGER
               = 0: successful exit
               < 0: if INFO = -k, the k-th argument had an illegal value



 LAPACK routine (version 3.1)    November 2006                       ZPTTRS(3)