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Declare constants at the native precision of MPAS #1282

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Feb 28, 2025
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Declare constants at the native precision of MPAS #1282

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7fcc9dd
Declare constants at the native precision of MPAS
kuanchihwang Nov 14, 2024
baebb48
Enforce `implicit none` at the module level of `mpas_constants`
kuanchihwang Jan 27, 2025
f37643e
Only `use` needed variables to avoid namespace pollution at the modul…
kuanchihwang Jan 27, 2025
9dd4113
Specify the accessibility of module variables in `mpas_constants`
kuanchihwang Jan 27, 2025
1353687
Clean up whitespaces in the `mpas_constants` module
kuanchihwang Jan 27, 2025
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53 changes: 38 additions & 15 deletions src/framework/mpas_constants.F
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Original file line number Diff line number Diff line change
Expand Up @@ -12,27 +12,33 @@
!> \brief MPAS Constant Module
!> \author Michael Duda
!> \date 03/27/13
!> \details
!> \details
!> This module provides various constants that can be used in different parts of MPAS.
!> They may or may not be a physical quantity.
!
!-----------------------------------------------------------------------

module mpas_constants

use mpas_kind_types
use mpas_kind_types, only: RKIND

implicit none

public
private :: RKIND

#ifdef MPAS_CAM_DYCORE
use physconst, only : pii => pi
use physconst, only : gravity => gravit
use physconst, only : omega
use physconst, only : a => rearth
use physconst, only : cp => cpair
use physconst, only : rgas => rair
use physconst, only : rv => rh2o
real (kind=RKIND) :: rvord = huge(1.0_RKIND) ! Derived in mpas_constants_compute_derived
real (kind=RKIND) :: cv = huge(1.0_RKIND) ! Derived in mpas_constants_compute_derived
real (kind=RKIND) :: cvpm = huge(1.0_RKIND) ! Derived in mpas_constants_compute_derived
! Set at run-time by `mpas_constants_compute_derived`.
real (kind=RKIND), protected :: pii = huge(1.0_RKIND)
real (kind=RKIND), protected :: a = huge(1.0_RKIND)
real (kind=RKIND), protected :: omega = huge(1.0_RKIND)
real (kind=RKIND), protected :: gravity = huge(1.0_RKIND)
real (kind=RKIND), protected :: rgas = huge(1.0_RKIND)
real (kind=RKIND), protected :: rv = huge(1.0_RKIND)
real (kind=RKIND), protected :: cp = huge(1.0_RKIND)
real (kind=RKIND), protected :: rvord = huge(1.0_RKIND)
real (kind=RKIND), protected :: cv = huge(1.0_RKIND)
real (kind=RKIND), protected :: cvpm = huge(1.0_RKIND)
#else
real (kind=RKIND), parameter :: pii = 3.141592653589793_RKIND !< Constant: Pi
real (kind=RKIND), parameter :: a = 6371229.0_RKIND !< Constant: Spherical Earth radius [m]
Expand All @@ -49,6 +55,7 @@ module mpas_constants
real (kind=RKIND), parameter :: p0 = 1.0e5_RKIND !< Constant: 100000 Pa
real (kind=RKIND), parameter :: prandtl = 1.0_RKIND !< Constant: Prandtl number


contains


Expand All @@ -59,7 +66,7 @@ module mpas_constants
!> \brief Computes derived constants
!> \author Michael Duda
!> \date 8 May 2020
!> \details
!> \details
!> This routine provides a place where physical constants provided by
!> the mpas_constants module may be computed at runtime. For example,
!> if some constants depend on namelist options or other runtime
Expand All @@ -74,9 +81,25 @@ module mpas_constants
!-----------------------------------------------------------------------
subroutine mpas_constants_compute_derived()

implicit none

#ifdef MPAS_CAM_DYCORE
use physconst, only: external_pii => pi
use physconst, only: external_a => rearth
use physconst, only: external_omega => omega
use physconst, only: external_gravity => gravit
use physconst, only: external_rgas => rair
use physconst, only: external_rv => rh2o
use physconst, only: external_cp => cpair

! Convert external constants to the native precision of MPAS (i.e., `RKIND`).

pii = real(external_pii, RKIND)
a = real(external_a, RKIND)
omega = real(external_omega, RKIND)
gravity = real(external_gravity, RKIND)
rgas = real(external_rgas, RKIND)
rv = real(external_rv, RKIND)
cp = real(external_cp, RKIND)

!
! In the case of CAM-MPAS, rgas may depend on a CAM namelist option,
! so physical constants that depend on rgas must be computed here after
Expand Down