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dpttrs

 NAME
      DPTTRS - solve a system of linear equations A * X = B with a
      symmetric positive definite tridiagonal matrix A using the
      factorization A = L*D*L**T or A = U**T*D*U computed by
      DPTTRF

 SYNOPSIS
      SUBROUTINE DPTTRS( N, NRHS, D, E, B, LDB, INFO )

          INTEGER        INFO, LDB, N, NRHS

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

 PURPOSE
      DPTTRS solves a system of linear equations A * X = B with a
      symmetric positive definite tridiagonal matrix A using the
      factorization A = L*D*L**T or A = U**T*D*U computed by
      DPTTRF.  (The two forms are equivalent if A is real.)

 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 factorization computed by DPTTRF.

      E       (input) DOUBLE PRECISION array, dimension (N-1)
              The (n-1) off-diagonal elements of the unit bidiago-
              nal factor U or L from the factorization computed by
              DPTTRF.

 (LDB,NRHS)
      B       (input/output) DOUBLE PRECISION array, dimension
              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 illegal
              value