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NAME
     zpttrs - solve a system of linear equations A * X = B with a
     Hermitian  positive  definite tridiagonal matrix A using the
     factorization A = U**H*D*U  or  A  =  L*D*L**H  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( * )



     #include <sunperf.h>

     void zpttrs(char uplo, int n, int  nrhs,  double  *d,  doub-
               lecomplex  *e,  doublecomplex  *zb,  int  ldb, int
               *info) ;

PURPOSE
     ZPTTRS solves a system of linear equations A * X = B with  a
     Hermitian  positive  definite tridiagonal matrix A using the
     factorization A = U**H*D*U  or  A  =  L*D*L**H  computed  by
     ZPTTRF.


ARGUMENTS
     UPLO      (input) CHARACTER*1
               Specifies whether the superdiagonal or the  subdi-
               agonal  of  the tridiagonal matrix A is stored and
               the form of the factorization:
               = 'U':  E is the  superdiagonal  of  U,  and  A  =
               U'*D*U;
               = 'L':  E is the subdiagonal of L, and A = L*D*L'.
               (The two forms are equivalent if A is real.)

     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 factorization computed by ZPTTRF.

     E         (input) COMPLEX*16 array, dimension (N-1)
               The (n-1) off-diagonal elements of the unit  bidi-
               agonal  factor  U or L from the factorization com-
               puted by ZPTTRF (see UPLO).

     B         (input/output) DOUBLE PRECISION  array,  dimension
               (LDB,NRHS)
               On entry, the right hand side matrix B.  On  exit,
               the solution matrix X.

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

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

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