SPTTRS (3lapack)

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 SPTTRF

SYNOPSIS

  SUBROUTINE SPTTRS( N, NRHS, D, E, B, LDB, INFO )

      INTEGER        INFO, LDB, N, NRHS

      REAL           B( LDB, * ), D( * ), E( * )

PURPOSE

  SPTTRS 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 SPTTRF.  (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) REAL array, dimension (N)
          The n diagonal elements of the diagonal matrix D from the
          factorization computed by SPTTRF.

  E       (input) REAL array, dimension (N-1)
          The (n-1) off-diagonal elements of the unit bidiagonal factor U or
          L from the factorization computed by SPTTRF.

  B       (input/output) REAL 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 illegal value