SGTTRS (3lapack)

solve one of the systems of equations A*X = B or A'*X = B,

SYNOPSIS

  SUBROUTINE SGTTRS( TRANS, N, NRHS, DL, D, DU, DU2, IPIV, B, LDB, INFO )

      CHARACTER      TRANS

      INTEGER        INFO, LDB, N, NRHS

      INTEGER        IPIV( * )

      REAL           B( LDB, * ), D( * ), DL( * ), DU( * ), DU2( * )

PURPOSE

  SGTTRS solves one of the systems of equations
     A*X = B  or  A'*X = B, with a tridiagonal matrix A using the LU
  factorization computed by SGTTRF.

ARGUMENTS

  TRANS   (input) CHARACTER
          Specifies the form of the system of equations:
          = 'N':  A * X = B  (No transpose)
          = 'T':  A'* X = B  (Transpose)
          = 'C':  A'* X = B  (Conjugate transpose = Transpose)

  N       (input) INTEGER
          The order of the 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.

  DL      (input) REAL array, dimension (N-1)
          The (n-1) multipliers that define the matrix L from the LU
          factorization of A.

  D       (input) REAL array, dimension (N)
          The n diagonal elements of the upper triangular matrix U from the
          LU factorization of A.

  DU      (input) REAL array, dimension (N-1)
          The (n-1) elements of the first superdiagonal of U.

  DU2     (input) REAL array, dimension (N-2)
          The (n-2) elements of the second superdiagonal of U.

  IPIV    (input) INTEGER array, dimension (N)
          The pivot indices; for 1 <= i <= n, row i of the matrix was
          interchanged with row IPIV(i).  IPIV(i) will always be either i or
          i+1; IPIV(i) = i indicates a row interchange was not required.

  B       (input/output) REAL array, dimension (LDB,NRHS)
          On entry, the right hand side matrix B.  On exit, B is overwritten
          by 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