CPTTRS (3lapack)

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 CPTTRF

SYNOPSIS

  SUBROUTINE CPTTRS( UPLO, N, NRHS, D, E, B, LDB, INFO )

      CHARACTER      UPLO

      INTEGER        INFO, LDB, N, NRHS

      REAL           D( * )

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

PURPOSE

  CPTTRS 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 CPTTRF.

ARGUMENTS

  UPLO    (input) CHARACTER*1
          Specifies whether the superdiagonal or the subdiagonal 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) REAL array, dimension (N)
          The n diagonal elements of the diagonal matrix D from the
          factorization computed by CPTTRF.

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

  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