| 1 | !> @file timestep.f90 |
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| 2 | !------------------------------------------------------------------------------! |
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| 3 | ! This file is part of PALM. |
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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 1997-2017 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 2119 2017-01-17 16:51:50Z hoffmann $ |
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| 27 | ! |
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| 28 | ! 2118 2017-01-17 16:38:49Z raasch |
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| 29 | ! OpenACC directives and related part of code removed |
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| 30 | ! |
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| 31 | ! 2000 2016-08-20 18:09:15Z knoop |
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| 32 | ! Forced header and separation lines into 80 columns |
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| 33 | ! |
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| 34 | ! 1849 2016-04-08 11:33:18Z hoffmann |
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| 35 | ! Adapted for modularization of microphysics |
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| 36 | ! |
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| 37 | ! 1682 2015-10-07 23:56:08Z knoop |
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| 38 | ! Code annotations made doxygen readable |
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| 39 | ! |
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| 40 | ! 1484 2014-10-21 10:53:05Z kanani |
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| 41 | ! Changes due to new module structure of the plant canopy model: |
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| 42 | ! calculations and parameters related to the plant canopy model removed |
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| 43 | ! (the limitation of the canopy drag, i.e. that the canopy drag itself should |
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| 44 | ! not change the sign of the velocity components, is now assured for in the |
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| 45 | ! calculation of the canopy tendency terms in subroutine plant_canopy_model) |
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| 46 | ! |
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| 47 | ! 1342 2014-03-26 17:04:47Z kanani |
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| 48 | ! REAL constants defined as wp-kind |
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| 49 | ! |
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| 50 | ! 1322 2014-03-20 16:38:49Z raasch |
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| 51 | ! REAL functions provided with KIND-attribute |
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| 52 | ! |
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| 53 | ! 1320 2014-03-20 08:40:49Z raasch |
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| 54 | ! ONLY-attribute added to USE-statements, |
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| 55 | ! kind-parameters added to all INTEGER and REAL declaration statements, |
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| 56 | ! kinds are defined in new module kinds, |
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| 57 | ! old module precision_kind is removed, |
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| 58 | ! revision history before 2012 removed, |
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| 59 | ! comment fields (!:) to be used for variable explanations added to |
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| 60 | ! all variable declaration statements |
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| 61 | ! |
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| 62 | ! 1257 2013-11-08 15:18:40Z raasch |
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| 63 | ! openacc porting |
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| 64 | ! bugfix for calculation of advective timestep in case of vertically stretched |
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| 65 | ! grids |
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| 66 | ! |
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| 67 | ! 1092 2013-02-02 11:24:22Z raasch |
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| 68 | ! unused variables removed |
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| 69 | ! |
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| 70 | ! 1053 2012-11-13 17:11:03Z hoffmann |
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| 71 | ! timestep is reduced in two-moment cloud scheme according to the maximum |
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| 72 | ! terminal velocity of rain drops |
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| 73 | ! |
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| 74 | ! 1036 2012-10-22 13:43:42Z raasch |
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| 75 | ! code put under GPL (PALM 3.9) |
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| 76 | ! |
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| 77 | ! 1001 2012-09-13 14:08:46Z raasch |
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| 78 | ! all actions concerning leapfrog scheme removed |
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| 79 | ! |
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| 80 | ! 978 2012-08-09 08:28:32Z fricke |
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| 81 | ! restriction of the outflow damping layer in the diffusion criterion removed |
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| 82 | ! |
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| 83 | ! 866 2012-03-28 06:44:41Z raasch |
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| 84 | ! bugfix for timestep calculation in case of Galilei transformation, |
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| 85 | ! special treatment in case of mirror velocity boundary condition removed |
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| 86 | ! |
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| 87 | ! Revision 1.1 1997/08/11 06:26:19 raasch |
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| 88 | ! Initial revision |
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| 89 | ! |
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| 90 | ! |
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| 91 | ! Description: |
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| 92 | ! ------------ |
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| 93 | !> Compute the time step under consideration of the FCL and diffusion criterion. |
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| 94 | !------------------------------------------------------------------------------! |
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| 95 | SUBROUTINE timestep |
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| 96 | |
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| 97 | |
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| 98 | USE arrays_3d, & |
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| 99 | ONLY: dzu, dzw, kh, km, u, v, w |
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| 100 | |
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| 101 | USE control_parameters, & |
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| 102 | ONLY: cfl_factor, coupling_mode, dt_3d, dt_fixed, dt_max, & |
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| 103 | galilei_transformation, old_dt, message_string, & |
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| 104 | stop_dt, terminate_coupled, terminate_coupled_remote, & |
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| 105 | timestep_reason, u_gtrans, use_ug_for_galilei_tr, v_gtrans |
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| 106 | |
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| 107 | USE cpulog, & |
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| 108 | ONLY: cpu_log, log_point |
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| 109 | |
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| 110 | USE grid_variables, & |
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| 111 | ONLY: dx, dx2, dy, dy2 |
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| 112 | |
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| 113 | USE indices, & |
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| 114 | ONLY: nxl, nxlg, nxr, nxrg, nyn, nyng, nys, nysg, nzb, nzt |
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| 115 | |
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| 116 | USE interfaces |
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| 117 | |
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| 118 | USE kinds |
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| 119 | |
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| 120 | USE microphysics_mod, & |
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| 121 | ONLY: dt_precipitation |
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| 122 | |
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| 123 | USE pegrid |
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| 124 | |
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| 125 | USE statistics, & |
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| 126 | ONLY: flow_statistics_called, hom, u_max, u_max_ijk, v_max, v_max_ijk,& |
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| 127 | w_max, w_max_ijk |
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| 128 | |
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| 129 | IMPLICIT NONE |
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| 130 | |
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| 131 | INTEGER(iwp) :: i !< |
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| 132 | INTEGER(iwp) :: j !< |
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| 133 | INTEGER(iwp) :: k !< |
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| 134 | |
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| 135 | REAL(wp) :: div !< |
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| 136 | REAL(wp) :: dt_diff !< |
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| 137 | REAL(wp) :: dt_diff_l !< |
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| 138 | REAL(wp) :: dt_u !< |
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| 139 | REAL(wp) :: dt_u_l !< |
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| 140 | REAL(wp) :: dt_v !< |
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| 141 | REAL(wp) :: dt_v_l !< |
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| 142 | REAL(wp) :: dt_w !< |
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| 143 | REAL(wp) :: dt_w_l !< |
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| 144 | REAL(wp) :: u_gtrans_l !< |
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| 145 | REAL(wp) :: u_max_l !< |
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| 146 | REAL(wp) :: u_min_l !< |
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| 147 | REAL(wp) :: value !< |
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| 148 | REAL(wp) :: v_gtrans_l !< |
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| 149 | REAL(wp) :: v_max_l !< |
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| 150 | REAL(wp) :: v_min_l !< |
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| 151 | REAL(wp) :: w_max_l !< |
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| 152 | REAL(wp) :: w_min_l !< |
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| 153 | |
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| 154 | REAL(wp), DIMENSION(2) :: uv_gtrans !< |
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| 155 | REAL(wp), DIMENSION(2) :: uv_gtrans_l !< |
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| 156 | REAL(wp), DIMENSION(3) :: reduce !< |
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| 157 | REAL(wp), DIMENSION(3) :: reduce_l !< |
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| 158 | REAL(wp), DIMENSION(nzb+1:nzt) :: dxyz2_min !< |
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| 159 | |
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| 160 | |
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| 161 | |
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| 162 | CALL cpu_log( log_point(12), 'calculate_timestep', 'start' ) |
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| 163 | |
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| 164 | ! |
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| 165 | !-- In case of Galilei-transform not using the geostrophic wind as translation |
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| 166 | !-- velocity, compute the volume-averaged horizontal velocity components, which |
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| 167 | !-- will then be subtracted from the horizontal wind for the time step and |
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| 168 | !-- horizontal advection routines. |
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| 169 | IF ( galilei_transformation .AND. .NOT. use_ug_for_galilei_tr ) THEN |
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| 170 | IF ( flow_statistics_called ) THEN |
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| 171 | ! |
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| 172 | !-- Horizontal averages already existent, just need to average them |
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| 173 | !-- vertically. |
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| 174 | u_gtrans = 0.0_wp |
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| 175 | v_gtrans = 0.0_wp |
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| 176 | DO k = nzb+1, nzt |
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| 177 | u_gtrans = u_gtrans + hom(k,1,1,0) |
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| 178 | v_gtrans = v_gtrans + hom(k,1,2,0) |
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| 179 | ENDDO |
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| 180 | u_gtrans = u_gtrans / REAL( nzt - nzb, KIND=wp ) |
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| 181 | v_gtrans = v_gtrans / REAL( nzt - nzb, KIND=wp ) |
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| 182 | ELSE |
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| 183 | ! |
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| 184 | !-- Averaging over the entire model domain. |
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| 185 | u_gtrans_l = 0.0_wp |
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| 186 | v_gtrans_l = 0.0_wp |
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| 187 | DO i = nxl, nxr |
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| 188 | DO j = nys, nyn |
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| 189 | DO k = nzb+1, nzt |
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| 190 | u_gtrans_l = u_gtrans_l + u(k,j,i) |
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| 191 | v_gtrans_l = v_gtrans_l + v(k,j,i) |
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| 192 | ENDDO |
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| 193 | ENDDO |
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| 194 | ENDDO |
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| 195 | uv_gtrans_l(1) = u_gtrans_l / REAL( (nxr-nxl+1)*(nyn-nys+1)*(nzt-nzb), KIND=wp ) |
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| 196 | uv_gtrans_l(2) = v_gtrans_l / REAL( (nxr-nxl+1)*(nyn-nys+1)*(nzt-nzb), KIND=wp ) |
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| 197 | #if defined( __parallel ) |
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| 198 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 199 | CALL MPI_ALLREDUCE( uv_gtrans_l, uv_gtrans, 2, MPI_REAL, MPI_SUM, & |
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| 200 | comm2d, ierr ) |
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| 201 | u_gtrans = uv_gtrans(1) / REAL( numprocs, KIND=wp ) |
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| 202 | v_gtrans = uv_gtrans(2) / REAL( numprocs, KIND=wp ) |
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| 203 | #else |
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| 204 | u_gtrans = uv_gtrans_l(1) |
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| 205 | v_gtrans = uv_gtrans_l(2) |
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| 206 | #endif |
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| 207 | ENDIF |
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| 208 | ENDIF |
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| 209 | |
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| 210 | ! |
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| 211 | !-- Determine the maxima of the velocity components, including their |
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| 212 | !-- grid index positions. |
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| 213 | CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, u, 'abs', 0.0_wp, & |
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| 214 | u_max, u_max_ijk ) |
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| 215 | CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, v, 'abs', 0.0_wp, & |
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| 216 | v_max, v_max_ijk ) |
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| 217 | CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, w, 'abs', 0.0_wp, & |
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| 218 | w_max, w_max_ijk ) |
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| 219 | |
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| 220 | IF ( .NOT. dt_fixed ) THEN |
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| 221 | ! |
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| 222 | !-- Variable time step: |
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| 223 | !-- Calculate the maximum time step according to the CFL-criterion, |
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| 224 | !-- individually for each velocity component |
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| 225 | dt_u_l = 999999.9_wp |
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| 226 | dt_v_l = 999999.9_wp |
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| 227 | dt_w_l = 999999.9_wp |
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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, ( dx / ( ABS( u(k,j,i) - u_gtrans ) + 1.0E-10_wp ) ) ) |
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| 232 | dt_v_l = MIN( dt_v_l, ( dy / ( ABS( v(k,j,i) - v_gtrans ) + 1.0E-10_wp ) ) ) |
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| 233 | dt_w_l = MIN( dt_w_l, ( dzu(k) / ( ABS( w(k,j,i) ) + 1.0E-10_wp ) ) ) |
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| 234 | ENDDO |
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| 235 | ENDDO |
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| 236 | ENDDO |
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| 237 | |
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| 238 | #if defined( __parallel ) |
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| 239 | reduce_l(1) = dt_u_l |
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| 240 | reduce_l(2) = dt_v_l |
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| 241 | reduce_l(3) = dt_w_l |
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| 242 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 243 | CALL MPI_ALLREDUCE( reduce_l, reduce, 3, MPI_REAL, MPI_MIN, comm2d, ierr ) |
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| 244 | dt_u = reduce(1) |
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| 245 | dt_v = reduce(2) |
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| 246 | dt_w = reduce(3) |
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| 247 | #else |
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| 248 | dt_u = dt_u_l |
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| 249 | dt_v = dt_v_l |
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| 250 | dt_w = dt_w_l |
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| 251 | #endif |
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| 252 | |
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| 253 | ! |
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| 254 | !-- Compute time step according to the diffusion criterion. |
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| 255 | !-- First calculate minimum grid spacing which only depends on index k |
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| 256 | !-- Note: also at k=nzb+1 a full grid length is being assumed, although |
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| 257 | !-- in the Prandtl-layer friction term only dz/2 is used. |
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| 258 | !-- Experience from the old model seems to justify this. |
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| 259 | dt_diff_l = 999999.0_wp |
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| 260 | |
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| 261 | DO k = nzb+1, nzt |
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| 262 | dxyz2_min(k) = MIN( dx2, dy2, dzw(k)*dzw(k) ) * 0.125_wp |
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| 263 | ENDDO |
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| 264 | |
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| 265 | !$OMP PARALLEL private(i,j,k,value) reduction(MIN: dt_diff_l) |
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| 266 | !$OMP DO |
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| 267 | DO i = nxl, nxr |
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| 268 | DO j = nys, nyn |
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| 269 | DO k = nzb+1, nzt |
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| 270 | dt_diff_l = MIN( dt_diff_l, dxyz2_min(k) / & |
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| 271 | ( MAX( kh(k,j,i), km(k,j,i) ) + 1E-20_wp ) ) |
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| 272 | ENDDO |
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| 273 | ENDDO |
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| 274 | ENDDO |
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| 275 | !$OMP END PARALLEL |
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| 276 | #if defined( __parallel ) |
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| 277 | IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr ) |
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| 278 | CALL MPI_ALLREDUCE( dt_diff_l, dt_diff, 1, MPI_REAL, MPI_MIN, comm2d, & |
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| 279 | ierr ) |
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| 280 | #else |
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| 281 | dt_diff = dt_diff_l |
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| 282 | #endif |
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| 283 | |
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| 284 | ! |
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| 285 | !-- The time step is the minimum of the 3-4 components and the diffusion time |
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| 286 | !-- step minus a reduction (cfl_factor) to be on the safe side. |
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| 287 | !-- The time step must not exceed the maximum allowed value. |
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| 288 | dt_3d = cfl_factor * MIN( dt_diff, dt_u, dt_v, dt_w, & |
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| 289 | dt_precipitation ) |
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| 290 | dt_3d = MIN( dt_3d, dt_max ) |
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| 291 | |
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| 292 | ! |
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| 293 | !-- Remember the restricting time step criterion for later output. |
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| 294 | IF ( MIN( dt_u, dt_v, dt_w ) < dt_diff ) THEN |
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| 295 | timestep_reason = 'A' |
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| 296 | ELSE |
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| 297 | timestep_reason = 'D' |
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| 298 | ENDIF |
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| 299 | |
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| 300 | ! |
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| 301 | !-- Set flag if the time step becomes too small. |
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| 302 | IF ( dt_3d < ( 0.00001_wp * dt_max ) ) THEN |
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| 303 | stop_dt = .TRUE. |
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| 304 | |
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| 305 | WRITE( message_string, * ) 'Time step has reached minimum limit.', & |
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| 306 | '&dt = ', dt_3d, ' s Simulation is terminated.', & |
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| 307 | '&old_dt = ', old_dt, ' s', & |
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| 308 | '&dt_u = ', dt_u, ' s', & |
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| 309 | '&dt_v = ', dt_v, ' s', & |
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| 310 | '&dt_w = ', dt_w, ' s', & |
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| 311 | '&dt_diff = ', dt_diff, ' s', & |
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| 312 | '&u_max = ', u_max, ' m/s k=', u_max_ijk(1), & |
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| 313 | ' j=', u_max_ijk(2), ' i=', u_max_ijk(3), & |
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| 314 | '&v_max = ', v_max, ' m/s k=', v_max_ijk(1), & |
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| 315 | ' j=', v_max_ijk(2), ' i=', v_max_ijk(3), & |
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| 316 | '&w_max = ', w_max, ' m/s k=', w_max_ijk(1), & |
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| 317 | ' j=', w_max_ijk(2), ' i=', w_max_ijk(3) |
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| 318 | CALL message( 'timestep', 'PA0312', 0, 1, 0, 6, 0 ) |
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| 319 | ! |
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| 320 | !-- In case of coupled runs inform the remote model of the termination |
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| 321 | !-- and its reason, provided the remote model has not already been |
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| 322 | !-- informed of another termination reason (terminate_coupled > 0) before. |
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| 323 | #if defined( __parallel ) |
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| 324 | IF ( coupling_mode /= 'uncoupled' .AND. terminate_coupled == 0 ) THEN |
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| 325 | terminate_coupled = 2 |
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| 326 | IF ( myid == 0 ) THEN |
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| 327 | CALL MPI_SENDRECV( & |
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| 328 | terminate_coupled, 1, MPI_INTEGER, target_id, 0, & |
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| 329 | terminate_coupled_remote, 1, MPI_INTEGER, target_id, 0, & |
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| 330 | comm_inter, status, ierr ) |
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| 331 | ENDIF |
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| 332 | CALL MPI_BCAST( terminate_coupled_remote, 1, MPI_INTEGER, 0, comm2d, ierr) |
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| 333 | ENDIF |
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| 334 | #endif |
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| 335 | ENDIF |
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| 336 | |
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| 337 | ! |
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| 338 | !-- Ensure a smooth value (two significant digits) of the timestep. |
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| 339 | div = 1000.0_wp |
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| 340 | DO WHILE ( dt_3d < div ) |
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| 341 | div = div / 10.0_wp |
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| 342 | ENDDO |
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| 343 | dt_3d = NINT( dt_3d * 100.0_wp / div ) * div / 100.0_wp |
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| 344 | |
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| 345 | ! |
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| 346 | !-- Adjust the time step |
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| 347 | old_dt = dt_3d |
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| 348 | |
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| 349 | ENDIF |
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| 350 | |
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| 351 | CALL cpu_log( log_point(12), 'calculate_timestep', 'stop' ) |
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| 352 | |
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| 353 | END SUBROUTINE timestep |
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