!-------------------------------------- LICENCE BEGIN ------------------------------------
!Environment Canada - Atmospheric Science and Technology License/Disclaimer,
!                     version 3; Last Modified: May 7, 2008.
!This is free but copyrighted software; you can use/redistribute/modify it under the terms
!of the Environment Canada - Atmospheric Science and Technology License/Disclaimer
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!
!This software is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY;
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!
!
!  X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X X
!

      subroutine invhelmcm(psol,prhs,pgam0,cdgrid,kfi) 2,2
!
!**s/r invhelmcm  - Inverts the Constant-coefficient Helmholtz operator.
!
!
!Author  : Luc Fillion - MSC - 10 March 04.
!Revision:
!  Luc Fillion - ARMA/EC - 29 May 2007 - Use precomputed tridiagonal matrices.
!
!     -------------------
!
!Arguments
!
      IMPLICIT NONE
!
#include "taglam4d.cdk"
#include "comdim.cdk"
#include "comgrd_param.cdk"
#include "comlun.cdk"
#include "comgemla.cdk"
!
      character*1 cdgrid
      integer kfi
      real*8 pgam0
      real*8 psol(nj)
      real*8 prhs(nj)
!
      integer jj
      real*8 zbx(nj)
!
!!
      if(cdgrid.eq.'S') then
        do jj=1,nj
          zbx(jj)=btris(jj,kfi) + pgam0
        enddo
        call cyclic(psol,prhs,atris,zbx,ctris,nj)
      else if(cdgrid.eq.'P') then
        do jj=1,nj
          zbx(jj)=btrip(jj,kfi) + pgam0
        call cyclic(psol,prhs,atrip,zbx,ctrip,nj)
        enddo
      endif
!
      return
      end