!***********************************************************************
!*                   GNU Lesser General Public License
!*
!* This file is part of the GFDL Flexible Modeling System (FMS).
!*
!* FMS is free software: you can redistribute it and/or modify it under
!* the terms of the GNU Lesser General Public License as published by
!* the Free Software Foundation, either version 3 of the License, or (at
!* your option) any later version.
!*
!* FMS is distributed in the hope that it will be useful, but WITHOUT
!* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
!* FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
!* for more details.
!*
!* You should have received a copy of the GNU Lesser General Public
!* License along with FMS.  If not, see <http://www.gnu.org/licenses/>.
!***********************************************************************
#ifdef __sgi
#define SYSTEM_CLOCK system_clock_sgi
!#######################################################################
  !mimics F90 SYSTEM_CLOCK intrinsic
subroutine system_clock_sgi( count, count_rate, count_max )
  integer(LONG_KIND), intent(out), optional :: count, count_rate, count_max
  integer(LONG_KIND) :: sgi_tick, sgi_ticks_per_sec, sgi_max_tick
  !sgi_max_tick currently returns 64
  !count must return a number between 0 and count_max
  integer(LONG_KIND), save :: maxtick=0
  if( maxtick.EQ.0 )then
     maxtick = sgi_max_tick() !actually reports #bits in maxtick
     if( maxtick.LT.BIT_SIZE(maxtick) )then
        maxtick = 2**maxtick
     else
        maxtick = huge(maxtick)
     end if
  end if
  if( PRESENT(count) )then
     count = modulo( sgi_tick()-tick0, maxtick )
     !          count = sgi_tick()
  end if
  if( PRESENT(count_rate) )then
     count_rate = sgi_ticks_per_sec()
  end if
  if( PRESENT(count_max) )then
     count_max = maxtick-1
  end if
  return
end subroutine system_clock_sgi

#elif defined(use_libMPI)
#define SYSTEM_CLOCK system_clock_mpi

!#######################################################################
subroutine system_clock_mpi( count, count_rate, count_max )
! There can be one ONE baseline count0 and this routine is
! included in multiple places.
!mimics F90 SYSTEM_CLOCK intrinsic
      integer(LONG_KIND), intent(out), optional :: count, count_rate, count_max
!count must return a number between 0 and count_max
      integer(LONG_KIND), parameter :: maxtick=HUGE(count_max)
      if(first_call_system_clock_mpi)then
         first_call_system_clock_mpi=.false.
         mpi_count0 = MPI_WTime()
         mpi_tick_rate = 1.d0/MPI_WTick()
      endif
      if( PRESENT(count) )then
          count = (MPI_WTime()-mpi_count0)*mpi_tick_rate
      end if
      if( PRESENT(count_rate) )then
          count_rate = mpi_tick_rate
      end if
      if( PRESENT(count_max) )then
          count_max = maxtick-1
      end if
      return
    end subroutine system_clock_mpi

#else
#define SYSTEM_CLOCK system_clock_default
subroutine system_clock_default( count, count_rate, count_max )
!mimics F90 SYSTEM_CLOCK intrinsic
      integer(LONG_KIND), optional :: count, count_rate, count_max
!count must return a number between 0 and count_max
      integer                      :: count_int, count_rate_int, count_max_int
      call system_clock( count_int, count_rate_int, count_max_int)
      if( PRESENT(count) )      count      = count_int
      if( PRESENT(count_rate) ) count_rate = count_rate_int
      if( PRESENT(count_max) )  count_max  = count_max_int
      return
    end subroutine system_clock_default
#endif