tridiag_solver.F90

subroutine clm_tridia (n, a, b, c, r, u )

!=========================================================================
!
!  CLMCLMCLMCLMCLMCLMCLMCLMCL  A community developed and sponsored, freely   
!  L                        M  available land surface process model.  
!  M --COMMON LAND MODEL--  C  
!  C                        L  CLM WEB INFO: http://clm.gsfc.nasa.gov
!  LMCLMCLMCLMCLMCLMCLMCLMCLM  CLM ListServ/Mailing List: 
!
!=========================================================================
! DESCRIPTION:
!
! REVISION HISTORY:
!  15 September 1999: Yongjiu Dai; Initial code
!  15 December 1999:  Paul Houser and Jon Radakovich; F90 Revision 
!  15 January 2002: Ian Baker revision to work in SiB
!=========================================================================
! $Id: tridiag_solver.F90,v 1.1 2005/04/06 22:24:04 chorak Exp $
!=========================================================================

    use kinds
    implicit none

    !=== Arguments ===========================================================

    integer , intent(in)  :: n
    real(kind=dbl_kind), intent(in)  :: a(1:n),b(1:n),c(1:n),r(1:n)
    real(kind=dbl_kind), intent(out) :: u(1:n)

    !=== Local Variables =====================================================

    integer j
    real(kind=dbl_kind) gam(1:n),bet

    !=== End Variable List ===================================================


    bet  = b(1)
    u(1) = r(1) / bet
    do j = 2, n
        gam(j) = c(j-1) / bet
        bet = b(j) - a(j) * gam(j)
        u(j) = (r(j) - a(j)*u(j-1)) / bet
    enddo

    do j = n-1, 1, -1
        u(j) = u(j) - gam(j+1) * u(j+1)
    enddo

end subroutine clm_tridia