SYNOPSIS
 SUBROUTINE SPTTRS(
 N, NRHS, D, E, B, LDB, INFO )
 INTEGER INFO, LDB, N, NRHS
 REAL B( LDB, * ), D( * ), E( * )
PURPOSE
SPTTRS solves a tridiagonal system of the formA * 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) 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) REAL array, dimension (N)
 The n diagonal elements of the diagonal matrix D from the L*D*L' factorization of A.
 E (input) REAL array, dimension (N1)
 The (n1) 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) REAL array, dimension (LDB,NRHS)
 On entry, the right hand side vectors B for the system of linear 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 kth argument had an illegal value