| 1 | !> @file timestep.f90 |
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| 2 | !------------------------------------------------------------------------------! |
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| 3 | ! This file is part of the PALM model system. |
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| 4 | ! |
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| 5 | ! PALM is free software: you can redistribute it and/or modify it under the |
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| 6 | ! terms of the GNU General Public License as published by the Free Software |
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| 7 | ! Foundation, either version 3 of the License, or (at your option) any later |
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| 8 | ! version. |
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| 9 | ! |
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| 10 | ! PALM is distributed in the hope that it will be useful, but WITHOUT ANY |
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| 11 | ! WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR |
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| 12 | ! A PARTICULAR PURPOSE. See the GNU General Public License for more details. |
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| 13 | ! |
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| 14 | ! You should have received a copy of the GNU General Public License along with |
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| 15 | ! PALM. If not, see <http://www.gnu.org/licenses/>. |
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| 16 | ! |
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| 17 | ! Copyright 1997-2019 Leibniz Universitaet Hannover |
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| 18 | !------------------------------------------------------------------------------! |
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| 19 | ! |
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| 20 | ! Current revisions: |
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| 21 | ! ------------------ |
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| 22 | ! |
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| 23 | ! |
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| 24 | ! Former revisions: |
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| 25 | ! ----------------- |
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| 26 | ! $Id: timestep.f90 4182 2019-08-22 15:20:23Z gronemeier $ |
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| 27 | ! Corrected "Former revisions" section |
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| 28 | ! |
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| 29 | ! 4101 2019-07-17 15:14:26Z gronemeier |
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| 30 | ! - consider 2*Km within diffusion criterion as Km is considered twice within |
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| 31 | ! the diffusion of e, |
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| 32 | ! - in RANS mode, instead of considering each wind component individually use |
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| 33 | ! the wind speed of 3d wind vector in CFL criterion |
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| 34 | ! - do not limit the increase of dt based on its previous value in RANS mode |
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| 35 | ! |
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| 36 | ! 3658 2019-01-07 20:28:54Z knoop |
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| 37 | ! OpenACC port for SPEC |
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| 38 | ! |
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| 39 | ! Revision 1.1 1997/08/11 06:26:19 raasch |
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| 40 | ! Initial revision |
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| 41 | ! |
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| 42 | ! |
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| 43 | ! Description: |
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| 44 | ! ------------ |
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| 45 | !> Compute the time step under consideration of the FCL and diffusion criterion. |
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| 46 | !------------------------------------------------------------------------------! |
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| 47 | SUBROUTINE timestep |
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| 48 | |
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| 49 | |
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| 50 | USE arrays_3d, & |
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| 51 | ONLY: dzu, dzw, kh, km, u, u_stokes_zu, v, v_stokes_zu, w |
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| 52 | |
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| 53 | USE control_parameters, & |
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| 54 | ONLY: cfl_factor, coupling_mode, dt_3d, dt_fixed, dt_max, & |
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| 55 | galilei_transformation, message_string, rans_mode, & |
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| 56 | stop_dt, terminate_coupled, terminate_coupled_remote, & |
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| 57 | timestep_reason, u_gtrans, use_ug_for_galilei_tr, v_gtrans |
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| 58 | |
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| 59 | USE cpulog, & |
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| 60 | ONLY: cpu_log, log_point |
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| 61 | |
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| 62 | USE grid_variables, & |
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| 63 | ONLY: dx, dx2, dy, dy2 |
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| 64 | |
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| 65 | USE indices, & |
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| 66 | ONLY: nxl, nxlg, nxr, nxrg, nyn, nyng, nys, nysg, nzb, nzt |
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| 67 | |
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| 68 | USE interfaces |
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| 69 | |
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| 70 | USE kinds |
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| 71 | |
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| 72 | USE bulk_cloud_model_mod, & |
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| 73 | ONLY: dt_precipitation |
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| 74 | |
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| 75 | USE pegrid |
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| 76 | |
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| 77 | USE pmc_interface, & |
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| 78 | ONLY: nested_run |
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| 79 | |
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| 80 | USE statistics, & |
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| 81 | ONLY: flow_statistics_called, hom, u_max, u_max_ijk, v_max, v_max_ijk,& |
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| 82 | w_max, w_max_ijk |
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| 83 | |
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| 84 | USE vertical_nesting_mod, & |
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| 85 | ONLY: vnested, vnest_timestep_sync |
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| 86 | |
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| 87 | IMPLICIT NONE |
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| 88 | |
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| 89 | INTEGER(iwp) :: i !< |
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| 90 | INTEGER(iwp) :: j !< |
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| 91 | INTEGER(iwp) :: k !< |
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| 92 | INTEGER(iwp) :: km_max_ijk(3) = -1 !< index values (i,j,k) of location where km_max occurs |
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| 93 | INTEGER(iwp) :: kh_max_ijk(3) = -1 !< index values (i,j,k) of location where kh_max occurs |
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| 94 | |
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| 95 | LOGICAL :: stop_dt_local !< local switch for controlling the time stepping |
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| 96 | |
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| 97 | REAL(wp) :: div !< |
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| 98 | REAL(wp) :: dt_diff !< |
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| 99 | REAL(wp) :: dt_diff_l !< |
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| 100 | REAL(wp) :: dt_u !< |
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| 101 | REAL(wp) :: dt_u_l !< |
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| 102 | REAL(wp) :: dt_v !< |
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| 103 | REAL(wp) :: dt_v_l !< |
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| 104 | REAL(wp) :: dt_w !< |
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| 105 | REAL(wp) :: dt_w_l !< |
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| 106 | REAL(wp) :: km_max !< maximum of Km in entire domain |
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| 107 | REAL(wp) :: kh_max !< maximum of Kh in entire domain |
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| 108 | REAL(wp) :: u_gtrans_l !< |
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| 109 | REAL(wp) :: v_gtrans_l !< |
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| 110 | |
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| 111 | REAL(wp), DIMENSION(2) :: uv_gtrans !< |
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| 112 | REAL(wp), DIMENSION(2) :: uv_gtrans_l !< |
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| 113 | REAL(wp), DIMENSION(3) :: reduce !< |
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| 114 | REAL(wp), DIMENSION(3) :: reduce_l !< |
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| 115 | REAL(wp), DIMENSION(nzb+1:nzt) :: dxyz2_min !< |
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| 116 | !$ACC DECLARE CREATE(dxyz2_min) |
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| 117 | |
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| 118 | |
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| 119 | CALL cpu_log( log_point(12), 'calculate_timestep', 'start' ) |
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| 120 | |
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| 121 | !$ACC UPDATE & |
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| 122 | !$ACC HOST(u(nzb:nzt+1,nysg:nyng,nxlg:nxrg)) & |
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| 123 | !$ACC HOST(v(nzb:nzt+1,nysg:nyng,nxlg:nxrg)) & |
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| 124 | !$ACC HOST(w(nzb:nzt+1,nysg:nyng,nxlg:nxrg)) & |
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| 125 | !$ACC HOST(kh(nzb:nzt+1,nysg:nyng,nxlg:nxrg)) & |
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| 126 | !$ACC HOST(km(nzb:nzt+1,nysg:nyng,nxlg:nxrg)) |
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| 127 | |
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| 128 | ! |
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| 129 | !-- In case of Galilei-transform not using the geostrophic wind as translation |
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| 130 | !-- velocity, compute the volume-averaged horizontal velocity components, which |
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| 131 | !-- will then be subtracted from the horizontal wind for the time step and |
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| 132 | !-- horizontal advection routines. |
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| 133 | IF ( galilei_transformation .AND. .NOT. use_ug_for_galilei_tr ) THEN |
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| 134 | IF ( flow_statistics_called ) THEN |
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| 135 | ! |
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| 136 | !-- Horizontal averages already existent, just need to average them |
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| 137 | !-- vertically. |
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| 138 | u_gtrans = 0.0_wp |
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| 139 | v_gtrans = 0.0_wp |
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| 140 | DO k = nzb+1, nzt |
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| 141 | u_gtrans = u_gtrans + hom(k,1,1,0) |
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| 142 | v_gtrans = v_gtrans + hom(k,1,2,0) |
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| 143 | ENDDO |
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| 144 | u_gtrans = u_gtrans / REAL( nzt - nzb, KIND=wp ) |
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| 145 | v_gtrans = v_gtrans / REAL( nzt - nzb, KIND=wp ) |
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| 146 | ELSE |
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| 147 | ! |
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| 148 | !-- Averaging over the entire model domain. |
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| 149 | u_gtrans_l = 0.0_wp |
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| 150 | v_gtrans_l = 0.0_wp |
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| 151 | DO i = nxl, nxr |
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| 152 | DO j = nys, nyn |
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| 153 | DO k = nzb+1, nzt |
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| 154 | u_gtrans_l = u_gtrans_l + u(k,j,i) |
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| 155 | v_gtrans_l = v_gtrans_l + v(k,j,i) |
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| 156 | ENDDO |
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| 157 | ENDDO |
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| 158 | ENDDO |
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| 159 | uv_gtrans_l(1) = u_gtrans_l / & |
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| 160 | REAL( (nxr-nxl+1)*(nyn-nys+1)*(nzt-nzb), KIND=wp ) |
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| 161 | uv_gtrans_l(2) = v_gtrans_l / & |
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| 162 | REAL( (nxr-nxl+1)*(nyn-nys+1)*(nzt-nzb), KIND=wp ) |
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| 163 | #if defined( __parallel ) |
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| 164 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 165 | CALL MPI_ALLREDUCE( uv_gtrans_l, uv_gtrans, 2, MPI_REAL, MPI_SUM, & |
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| 166 | comm2d, ierr ) |
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| 167 | u_gtrans = uv_gtrans(1) / REAL( numprocs, KIND=wp ) |
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| 168 | v_gtrans = uv_gtrans(2) / REAL( numprocs, KIND=wp ) |
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| 169 | #else |
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| 170 | u_gtrans = uv_gtrans_l(1) |
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| 171 | v_gtrans = uv_gtrans_l(2) |
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| 172 | #endif |
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| 173 | ENDIF |
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| 174 | ENDIF |
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| 175 | |
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| 176 | ! |
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| 177 | !-- Determine the maxima of the velocity components, including their |
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| 178 | !-- grid index positions. |
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| 179 | CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, u, 'abs', 0.0_wp, & |
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| 180 | u_max, u_max_ijk ) |
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| 181 | CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, v, 'abs', 0.0_wp, & |
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| 182 | v_max, v_max_ijk ) |
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| 183 | CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, w, 'abs', 0.0_wp, & |
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| 184 | w_max, w_max_ijk ) |
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| 185 | |
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| 186 | IF ( .NOT. dt_fixed ) THEN |
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| 187 | ! |
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| 188 | !-- Variable time step: |
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| 189 | !-- Calculate the maximum time step according to the CFL-criterion |
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| 190 | dt_u_l = 999999.9_wp |
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| 191 | dt_v_l = 999999.9_wp |
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| 192 | dt_w_l = 999999.9_wp |
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| 193 | |
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| 194 | IF ( .NOT. rans_mode ) THEN |
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| 195 | ! |
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| 196 | !-- Consider each velocity component individually |
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| 197 | |
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| 198 | !$ACC PARALLEL LOOP COLLAPSE(3) PRIVATE(i,j,k) & |
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| 199 | !$ACC COPY(dt_u_l, dt_v_l, dt_w_l, u_stokes_zu, v_stokes_zu) & |
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| 200 | !$ACC REDUCTION(MIN: dt_u_l, dt_v_l, dt_w_l) & |
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| 201 | !$ACC PRESENT(u, v, w, dzu) |
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| 202 | DO i = nxl, nxr |
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| 203 | DO j = nys, nyn |
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| 204 | DO k = nzb+1, nzt |
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| 205 | dt_u_l = MIN( dt_u_l, ( dx / & |
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| 206 | ( ABS( u(k,j,i) - u_gtrans + u_stokes_zu(k) ) & |
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| 207 | + 1.0E-10_wp ) ) ) |
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| 208 | dt_v_l = MIN( dt_v_l, ( dy / & |
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| 209 | ( ABS( v(k,j,i) - v_gtrans + v_stokes_zu(k) ) & |
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| 210 | + 1.0E-10_wp ) ) ) |
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| 211 | dt_w_l = MIN( dt_w_l, ( dzu(k) / & |
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| 212 | ( ABS( w(k,j,i) ) + 1.0E-10_wp ) ) ) |
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| 213 | ENDDO |
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| 214 | ENDDO |
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| 215 | ENDDO |
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| 216 | |
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| 217 | ELSE |
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| 218 | ! |
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| 219 | !-- Consider the wind speed at the scalar-grid point |
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| 220 | !-- !> @note considering the wind speed instead of each individual wind |
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| 221 | !-- !> component is only a workaround so far. This might has to be |
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| 222 | !-- !> changed in the future. |
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| 223 | |
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| 224 | !$ACC PARALLEL LOOP COLLAPSE(3) PRIVATE(i,j,k) & |
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| 225 | !$ACC COPY(dt_u_l, u_stokes_zu, v_stokes_zu) & |
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| 226 | !$ACC REDUCTION(MIN: dt_u_l) & |
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| 227 | !$ACC PRESENT(u, v, w, dzu) |
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| 228 | DO i = nxl, nxr |
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| 229 | DO j = nys, nyn |
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| 230 | DO k = nzb+1, nzt |
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| 231 | dt_u_l = MIN( dt_u_l, ( MIN( dx, dy, dzu(k) ) / ( & |
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| 232 | SQRT( ( 0.5 * ( u(k,j,i) + u(k,j,i+1) ) - u_gtrans + u_stokes_zu(k) )**2 & |
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| 233 | + ( 0.5 * ( v(k,j,i) + v(k,j+1,i) ) - v_gtrans + v_stokes_zu(k) )**2 & |
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| 234 | + ( 0.5 * ( w(k,j,i) + w(k-1,j,i) ) )**2 ) & |
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| 235 | + 1.0E-10_wp ) ) ) |
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| 236 | ENDDO |
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| 237 | ENDDO |
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| 238 | ENDDO |
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| 239 | |
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| 240 | dt_v_l = dt_u_l |
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| 241 | dt_w_l = dt_u_l |
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| 242 | |
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| 243 | ENDIF |
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| 244 | |
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| 245 | #if defined( __parallel ) |
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| 246 | reduce_l(1) = dt_u_l |
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| 247 | reduce_l(2) = dt_v_l |
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| 248 | reduce_l(3) = dt_w_l |
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| 249 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 250 | CALL MPI_ALLREDUCE( reduce_l, reduce, 3, MPI_REAL, MPI_MIN, comm2d, ierr ) |
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| 251 | dt_u = reduce(1) |
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| 252 | dt_v = reduce(2) |
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| 253 | dt_w = reduce(3) |
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| 254 | #else |
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| 255 | dt_u = dt_u_l |
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| 256 | dt_v = dt_v_l |
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| 257 | dt_w = dt_w_l |
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| 258 | #endif |
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| 259 | |
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| 260 | ! |
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| 261 | !-- Compute time step according to the diffusion criterion. |
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| 262 | !-- First calculate minimum grid spacing which only depends on index k. |
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| 263 | !-- When using the dynamic subgrid model, negative km are possible. |
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| 264 | dt_diff_l = 999999.0_wp |
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| 265 | |
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| 266 | !$ACC PARALLEL LOOP PRESENT(dxyz2_min, dzw) |
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| 267 | DO k = nzb+1, nzt |
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| 268 | dxyz2_min(k) = MIN( dx2, dy2, dzw(k)*dzw(k) ) * 0.125_wp |
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| 269 | ENDDO |
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| 270 | |
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| 271 | !$OMP PARALLEL private(i,j,k) reduction(MIN: dt_diff_l) |
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| 272 | !$OMP DO |
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| 273 | !$ACC PARALLEL LOOP COLLAPSE(3) PRIVATE(i,j,k) & |
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| 274 | !$ACC COPY(dt_diff_l) REDUCTION(MIN: dt_diff_l) & |
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| 275 | !$ACC PRESENT(dxyz2_min, kh, km) |
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| 276 | DO i = nxl, nxr |
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| 277 | DO j = nys, nyn |
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| 278 | DO k = nzb+1, nzt |
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| 279 | dt_diff_l = MIN( dt_diff_l, & |
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| 280 | dxyz2_min(k) / & |
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| 281 | ( MAX( kh(k,j,i), 2.0_wp * ABS( km(k,j,i) ) ) & |
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| 282 | + 1E-20_wp ) ) |
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| 283 | ENDDO |
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| 284 | ENDDO |
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| 285 | ENDDO |
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| 286 | !$OMP END PARALLEL |
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| 287 | #if defined( __parallel ) |
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| 288 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 289 | CALL MPI_ALLREDUCE( dt_diff_l, dt_diff, 1, MPI_REAL, MPI_MIN, comm2d, & |
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| 290 | ierr ) |
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| 291 | #else |
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| 292 | dt_diff = dt_diff_l |
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| 293 | #endif |
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| 294 | |
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| 295 | ! |
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| 296 | !-- The time step is the minimum of the 3-4 components and the diffusion time |
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| 297 | !-- step minus a reduction (cfl_factor) to be on the safe side. |
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| 298 | !-- The time step must not exceed the maximum allowed value. |
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| 299 | dt_3d = cfl_factor * MIN( dt_diff, dt_u, dt_v, dt_w, dt_precipitation ) |
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| 300 | dt_3d = MIN( dt_3d, dt_max ) |
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| 301 | |
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| 302 | ! |
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| 303 | !-- Remember the restricting time step criterion for later output. |
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| 304 | IF ( MIN( dt_u, dt_v, dt_w ) < dt_diff ) THEN |
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| 305 | timestep_reason = 'A' |
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| 306 | ELSE |
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| 307 | timestep_reason = 'D' |
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| 308 | ENDIF |
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| 309 | |
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| 310 | ! |
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| 311 | !-- Set flag if the time step becomes too small. |
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| 312 | IF ( dt_3d < ( 0.00001_wp * dt_max ) ) THEN |
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| 313 | stop_dt = .TRUE. |
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| 314 | |
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| 315 | ! |
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| 316 | !-- Determine the maxima of the diffusion coefficients, including their |
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| 317 | !-- grid index positions. |
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| 318 | CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, km, 'abs', & |
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| 319 | 0.0_wp, km_max, km_max_ijk ) |
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| 320 | CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, kh, 'abs', & |
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| 321 | 0.0_wp, kh_max, kh_max_ijk ) |
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| 322 | |
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| 323 | WRITE( message_string, * ) 'Time step has reached minimum limit.', & |
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| 324 | '&dt = ', dt_3d, ' s Simulation is terminated.', & |
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| 325 | '&dt_u = ', dt_u, ' s', & |
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| 326 | '&dt_v = ', dt_v, ' s', & |
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| 327 | '&dt_w = ', dt_w, ' s', & |
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| 328 | '&dt_diff = ', dt_diff, ' s', & |
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| 329 | '&u_max = ', u_max, ' m/s k=', u_max_ijk(1), & |
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| 330 | ' j=', u_max_ijk(2), ' i=', u_max_ijk(3), & |
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| 331 | '&v_max = ', v_max, ' m/s k=', v_max_ijk(1), & |
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| 332 | ' j=', v_max_ijk(2), ' i=', v_max_ijk(3), & |
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| 333 | '&w_max = ', w_max, ' m/s k=', w_max_ijk(1), & |
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| 334 | ' j=', w_max_ijk(2), ' i=', w_max_ijk(3), & |
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| 335 | '&km_max = ', km_max, ' m2/s2 k=', km_max_ijk(1), & |
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| 336 | ' j=', km_max_ijk(2), ' i=', km_max_ijk(3), & |
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| 337 | '&kh_max = ', kh_max, ' m2/s2 k=', kh_max_ijk(1), & |
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| 338 | ' j=', kh_max_ijk(2), ' i=', kh_max_ijk(3) |
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| 339 | CALL message( 'timestep', 'PA0312', 0, 1, 0, 6, 0 ) |
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| 340 | ! |
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| 341 | !-- In case of coupled runs inform the remote model of the termination |
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| 342 | !-- and its reason, provided the remote model has not already been |
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| 343 | !-- informed of another termination reason (terminate_coupled > 0) before. |
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| 344 | #if defined( __parallel ) |
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| 345 | IF ( coupling_mode /= 'uncoupled' .AND. terminate_coupled == 0 ) THEN |
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| 346 | terminate_coupled = 2 |
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| 347 | IF ( myid == 0 ) THEN |
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| 348 | CALL MPI_SENDRECV( & |
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| 349 | terminate_coupled, 1, MPI_INTEGER, target_id, 0, & |
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| 350 | terminate_coupled_remote, 1, MPI_INTEGER, target_id, 0, & |
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| 351 | comm_inter, status, ierr ) |
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| 352 | ENDIF |
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| 353 | CALL MPI_BCAST( terminate_coupled_remote, 1, MPI_INTEGER, 0, & |
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| 354 | comm2d, ierr) |
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| 355 | ENDIF |
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| 356 | #endif |
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| 357 | ENDIF |
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| 358 | |
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| 359 | ! |
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| 360 | !-- In case of nested runs all parent/child processes have to terminate if |
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| 361 | !-- one process has set the stop flag, i.e. they need to set the stop flag |
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| 362 | !-- too. |
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| 363 | IF ( nested_run ) THEN |
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| 364 | stop_dt_local = stop_dt |
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| 365 | #if defined( __parallel ) |
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| 366 | CALL MPI_ALLREDUCE( stop_dt_local, stop_dt, 1, MPI_LOGICAL, MPI_LOR, & |
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| 367 | MPI_COMM_WORLD, ierr ) |
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| 368 | #endif |
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| 369 | ENDIF |
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| 370 | |
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| 371 | ! |
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| 372 | !-- Ensure a smooth value (two significant digits) of the timestep. |
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| 373 | div = 1000.0_wp |
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| 374 | DO WHILE ( dt_3d < div ) |
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| 375 | div = div / 10.0_wp |
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| 376 | ENDDO |
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| 377 | dt_3d = NINT( dt_3d * 100.0_wp / div ) * div / 100.0_wp |
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| 378 | |
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| 379 | ENDIF |
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| 380 | |
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| 381 | ! |
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| 382 | !-- Vertical nesting: coarse and fine grid timestep has to be identical |
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| 383 | IF ( vnested ) CALL vnest_timestep_sync |
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| 384 | |
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| 385 | CALL cpu_log( log_point(12), 'calculate_timestep', 'stop' ) |
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| 386 | |
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| 387 | END SUBROUTINE timestep |
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