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source: palm/trunk/SOURCE/timestep.f90 @ 3651

Last change on this file since 3651 was 3634, checked in by knoop, 6 years ago
OpenACC port for SPEC
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1	!> @file timestep.f90
2	!------------------------------------------------------------------------------!
3	! This file is part of the PALM model system.
4	!
5	! PALM is free software: you can redistribute it and/or modify it under the
6	! terms of the GNU General Public License as published by the Free Software
7	! Foundation, either version 3 of the License, or (at your option) any later
8	! version.
9	!
10	! PALM is distributed in the hope that it will be useful, but WITHOUT ANY
11	! WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
12	! A PARTICULAR PURPOSE. See the GNU General Public License for more details.
13	!
14	! You should have received a copy of the GNU General Public License along with
15	! PALM. If not, see <http://www.gnu.org/licenses/>.
16	!
17	! Copyright 1997-2018 Leibniz Universitaet Hannover
18	!------------------------------------------------------------------------------!
19	!
20	! Current revisions:
21	! ------------------
22	!
23	!
24	! Former revisions:
25	! -----------------
26	! $Id: timestep.f90 3634 2018-12-18 12:31:28Z suehring $
27	! OpenACC port for SPEC
28	!
29	! 3311 2018-10-05 12:34:56Z raasch
30	! Stokes drift is regarded in timestep calculation
31	!
32	! 3274 2018-09-24 15:42:55Z knoop
33	! Modularization of all bulk cloud physics code components
34	!
35	! 3241 2018-09-12 15:02:00Z raasch
36	! unused variables removed
37	!
38	! 3120 2018-07-11 18:30:57Z gronemeier
39	! Put ABS( km ) in computation of time step according to the diffusion criterion
40	!
41	! 3084 2018-06-19 15:30:55Z gronemeier
42	! limit increase of dt_3d only in case of RANS mode
43	!
44	! 3083 2018-06-19 14:03:12Z gronemeier
45	! limit dt_3d to be at maximum 2*old_dt; define old_dt at beginning of routine
46	! Add km/kh_max
47	!
48	! 3049 2018-05-29 13:52:36Z Giersch
49	! Error messages revised
50	!
51	! 3045 2018-05-28 07:55:41Z Giersch
52	! Error message revised
53	!
54	! 2718 2018-01-02 08:49:38Z maronga
55	! Corrected "Former revisions" section
56	!
57	! 2696 2017-12-14 17:12:51Z kanani
58	! Change in file header (GPL part)
59	!
60	! 2365 2017-08-21 14:59:59Z kanani
61	! Vertical grid nesting: Sync fine and coarse grid timestep (SadiqHuq)
62	!
63	! 2258 2017-06-08 07:55:13Z suehring
64	! Bugfix, add pre-preprocessor directives to enable non-parrallel mode
65	!
66	! 2168 2017-03-06 13:08:38Z suehring
67	!
68	! 2130 2017-01-24 16:25:39Z raasch
69	! bugfix: in case of nested runs the stop condition in case of too small
70	! timesteps is communicated to all parent/child processes,
71	! some formatting done
72	!
73	! 2118 2017-01-17 16:38:49Z raasch
74	! OpenACC directives and related part of code removed
75	!
76	! 2000 2016-08-20 18:09:15Z knoop
77	! Forced header and separation lines into 80 columns
78	!
79	! 1849 2016-04-08 11:33:18Z hoffmann
80	! Adapted for modularization of microphysics
81	!
82	! 1682 2015-10-07 23:56:08Z knoop
83	! Code annotations made doxygen readable
84	!
85	! 1484 2014-10-21 10:53:05Z kanani
86	! Changes due to new module structure of the plant canopy model:
87	! calculations and parameters related to the plant canopy model removed
88	! (the limitation of the canopy drag, i.e. that the canopy drag itself should
89	! not change the sign of the velocity components, is now assured for in the
90	! calculation of the canopy tendency terms in subroutine plant_canopy_model)
91	!
92	! 1342 2014-03-26 17:04:47Z kanani
93	! REAL constants defined as wp-kind
94	!
95	! 1322 2014-03-20 16:38:49Z raasch
96	! REAL functions provided with KIND-attribute
97	!
98	! 1320 2014-03-20 08:40:49Z raasch
99	! ONLY-attribute added to USE-statements,
100	! kind-parameters added to all INTEGER and REAL declaration statements,
101	! kinds are defined in new module kinds,
102	! old module precision_kind is removed,
103	! revision history before 2012 removed,
104	! comment fields (!:) to be used for variable explanations added to
105	! all variable declaration statements
106	!
107	! 1257 2013-11-08 15:18:40Z raasch
108	! openacc porting
109	! bugfix for calculation of advective timestep in case of vertically stretched
110	! grids
111	!
112	! 1092 2013-02-02 11:24:22Z raasch
113	! unused variables removed
114	!
115	! 1053 2012-11-13 17:11:03Z hoffmann
116	! timestep is reduced in two-moment cloud scheme according to the maximum
117	! terminal velocity of rain drops
118	!
119	! 1036 2012-10-22 13:43:42Z raasch
120	! code put under GPL (PALM 3.9)
121	!
122	! 1001 2012-09-13 14:08:46Z raasch
123	! all actions concerning leapfrog scheme removed
124	!
125	! 978 2012-08-09 08:28:32Z fricke
126	! restriction of the outflow damping layer in the diffusion criterion removed
127	!
128	! 866 2012-03-28 06:44:41Z raasch
129	! bugfix for timestep calculation in case of Galilei transformation,
130	! special treatment in case of mirror velocity boundary condition removed
131	!
132	! Revision 1.1 1997/08/11 06:26:19 raasch
133	! Initial revision
134	!
135	!
136	! Description:
137	! ------------
138	!> Compute the time step under consideration of the FCL and diffusion criterion.
139	!------------------------------------------------------------------------------!
140	SUBROUTINE timestep
141
142
143	USE arrays_3d, &
144	ONLY: dzu, dzw, kh, km, u, u_stokes_zu, v, v_stokes_zu, w
145
146	USE control_parameters, &
147	ONLY: cfl_factor, coupling_mode, dt_3d, dt_fixed, dt_max, &
148	galilei_transformation, old_dt, message_string, rans_mode, &
149	stop_dt, terminate_coupled, terminate_coupled_remote, &
150	timestep_reason, u_gtrans, use_ug_for_galilei_tr, v_gtrans
151
152	USE cpulog, &
153	ONLY: cpu_log, log_point
154
155	USE grid_variables, &
156	ONLY: dx, dx2, dy, dy2
157
158	USE indices, &
159	ONLY: nxl, nxlg, nxr, nxrg, nyn, nyng, nys, nysg, nzb, nzt
160
161	USE interfaces
162
163	USE kinds
164
165	USE bulk_cloud_model_mod, &
166	ONLY: dt_precipitation
167
168	USE pegrid
169
170	USE pmc_interface, &
171	ONLY: nested_run
172
173	USE statistics, &
174	ONLY: flow_statistics_called, hom, u_max, u_max_ijk, v_max, v_max_ijk,&
175	w_max, w_max_ijk
176
177	USE vertical_nesting_mod, &
178	ONLY: vnested, vnest_timestep_sync
179
180	IMPLICIT NONE
181
182	INTEGER(iwp) :: i !<
183	INTEGER(iwp) :: j !<
184	INTEGER(iwp) :: k !<
185	INTEGER(iwp) :: km_max_ijk(3) = -1 !< index values (i,j,k) of location where km_max occurs
186	INTEGER(iwp) :: kh_max_ijk(3) = -1 !< index values (i,j,k) of location where kh_max occurs
187
188	LOGICAL :: stop_dt_local !< local switch for controlling the time stepping
189
190	REAL(wp) :: div !<
191	REAL(wp) :: dt_diff !<
192	REAL(wp) :: dt_diff_l !<
193	REAL(wp) :: dt_u !<
194	REAL(wp) :: dt_u_l !<
195	REAL(wp) :: dt_v !<
196	REAL(wp) :: dt_v_l !<
197	REAL(wp) :: dt_w !<
198	REAL(wp) :: dt_w_l !<
199	REAL(wp) :: km_max !< maximum of Km in entire domain
200	REAL(wp) :: kh_max !< maximum of Kh in entire domain
201	REAL(wp) :: u_gtrans_l !<
202	REAL(wp) :: v_gtrans_l !<
203
204	REAL(wp), DIMENSION(2) :: uv_gtrans !<
205	REAL(wp), DIMENSION(2) :: uv_gtrans_l !<
206	REAL(wp), DIMENSION(3) :: reduce !<
207	REAL(wp), DIMENSION(3) :: reduce_l !<
208	REAL(wp), DIMENSION(nzb+1:nzt) :: dxyz2_min !<
209	!$ACC DECLARE CREATE(dxyz2_min)
210
211
212	CALL cpu_log( log_point(12), 'calculate_timestep', 'start' )
213	!
214	!-- Save former time step as reference
215	old_dt = dt_3d
216
217	!
218	!-- In case of Galilei-transform not using the geostrophic wind as translation
219	!-- velocity, compute the volume-averaged horizontal velocity components, which
220	!-- will then be subtracted from the horizontal wind for the time step and
221	!-- horizontal advection routines.
222	IF ( galilei_transformation .AND. .NOT. use_ug_for_galilei_tr ) THEN
223	IF ( flow_statistics_called ) THEN
224	!
225	!-- Horizontal averages already existent, just need to average them
226	!-- vertically.
227	u_gtrans = 0.0_wp
228	v_gtrans = 0.0_wp
229	DO k = nzb+1, nzt
230	u_gtrans = u_gtrans + hom(k,1,1,0)
231	v_gtrans = v_gtrans + hom(k,1,2,0)
232	ENDDO
233	u_gtrans = u_gtrans / REAL( nzt - nzb, KIND=wp )
234	v_gtrans = v_gtrans / REAL( nzt - nzb, KIND=wp )
235	ELSE
236	!
237	!-- Averaging over the entire model domain.
238	u_gtrans_l = 0.0_wp
239	v_gtrans_l = 0.0_wp
240	DO i = nxl, nxr
241	DO j = nys, nyn
242	DO k = nzb+1, nzt
243	u_gtrans_l = u_gtrans_l + u(k,j,i)
244	v_gtrans_l = v_gtrans_l + v(k,j,i)
245	ENDDO
246	ENDDO
247	ENDDO
248	uv_gtrans_l(1) = u_gtrans_l / &
249	REAL( (nxr-nxl+1)(nyn-nys+1)(nzt-nzb), KIND=wp )
250	uv_gtrans_l(2) = v_gtrans_l / &
251	REAL( (nxr-nxl+1)(nyn-nys+1)(nzt-nzb), KIND=wp )
252	#if defined( __parallel )
253	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
254	CALL MPI_ALLREDUCE( uv_gtrans_l, uv_gtrans, 2, MPI_REAL, MPI_SUM, &
255	comm2d, ierr )
256	u_gtrans = uv_gtrans(1) / REAL( numprocs, KIND=wp )
257	v_gtrans = uv_gtrans(2) / REAL( numprocs, KIND=wp )
258	#else
259	u_gtrans = uv_gtrans_l(1)
260	v_gtrans = uv_gtrans_l(2)
261	#endif
262	ENDIF
263	ENDIF
264
265	!
266	!-- Determine the maxima of the velocity components, including their
267	!-- grid index positions.
268	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, u, 'abs', 0.0_wp, &
269	u_max, u_max_ijk )
270	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, v, 'abs', 0.0_wp, &
271	v_max, v_max_ijk )
272	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, w, 'abs', 0.0_wp, &
273	w_max, w_max_ijk )
274
275	IF ( .NOT. dt_fixed ) THEN
276	!
277	!-- Variable time step:
278	!-- Calculate the maximum time step according to the CFL-criterion,
279	!-- individually for each velocity component
280	dt_u_l = 999999.9_wp
281	dt_v_l = 999999.9_wp
282	dt_w_l = 999999.9_wp
283	!$ACC PARALLEL LOOP COLLAPSE(3) PRIVATE(i,j,k) &
284	!$ACC COPY(dt_u_l, dt_v_l, dt_w_l, u_stokes_zu, v_stokes_zu) &
285	!$ACC REDUCTION(MIN: dt_u_l, dt_v_l, dt_w_l) &
286	!$ACC PRESENT(u, v, w, dzu)
287	DO i = nxl, nxr
288	DO j = nys, nyn
289	DO k = nzb+1, nzt
290	dt_u_l = MIN( dt_u_l, ( dx / &
291	( ABS( u(k,j,i) - u_gtrans + u_stokes_zu(k) ) &
292	+ 1.0E-10_wp ) ) )
293	dt_v_l = MIN( dt_v_l, ( dy / &
294	( ABS( v(k,j,i) - v_gtrans + v_stokes_zu(k) ) &
295	+ 1.0E-10_wp ) ) )
296	dt_w_l = MIN( dt_w_l, ( dzu(k) / &
297	( ABS( w(k,j,i) ) + 1.0E-10_wp ) ) )
298	ENDDO
299	ENDDO
300	ENDDO
301
302	#if defined( __parallel )
303	reduce_l(1) = dt_u_l
304	reduce_l(2) = dt_v_l
305	reduce_l(3) = dt_w_l
306	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
307	CALL MPI_ALLREDUCE( reduce_l, reduce, 3, MPI_REAL, MPI_MIN, comm2d, ierr )
308	dt_u = reduce(1)
309	dt_v = reduce(2)
310	dt_w = reduce(3)
311	#else
312	dt_u = dt_u_l
313	dt_v = dt_v_l
314	dt_w = dt_w_l
315	#endif
316
317	!
318	!-- Compute time step according to the diffusion criterion.
319	!-- First calculate minimum grid spacing which only depends on index k.
320	!-- When using the dynamic subgrid model, negative km are possible.
321	dt_diff_l = 999999.0_wp
322
323	!$ACC PARALLEL LOOP PRESENT(dxyz2_min, dzw)
324	DO k = nzb+1, nzt
325	dxyz2_min(k) = MIN( dx2, dy2, dzw(k)dzw(k) ) 0.125_wp
326	ENDDO
327
328	!$OMP PARALLEL private(i,j,k) reduction(MIN: dt_diff_l)
329	!$OMP DO
330	!$ACC PARALLEL LOOP COLLAPSE(3) PRIVATE(i,j,k) &
331	!$ACC COPY(dt_diff_l) REDUCTION(MIN: dt_diff_l) &
332	!$ACC PRESENT(dxyz2_min, kh, km)
333	DO i = nxl, nxr
334	DO j = nys, nyn
335	DO k = nzb+1, nzt
336	dt_diff_l = MIN( dt_diff_l, dxyz2_min(k) / &
337	( MAX( kh(k,j,i), ABS( km(k,j,i) ) ) &
338	+ 1E-20_wp ) )
339	ENDDO
340	ENDDO
341	ENDDO
342	!$OMP END PARALLEL
343	#if defined( __parallel )
344	IF ( collective_wait ) CALL MPI_BARRIER( comm2d, ierr )
345	CALL MPI_ALLREDUCE( dt_diff_l, dt_diff, 1, MPI_REAL, MPI_MIN, comm2d, &
346	ierr )
347	#else
348	dt_diff = dt_diff_l
349	#endif
350
351	!
352	!-- The time step is the minimum of the 3-4 components and the diffusion time
353	!-- step minus a reduction (cfl_factor) to be on the safe side.
354	!-- The time step must not exceed the maximum allowed value.
355	dt_3d = cfl_factor * MIN( dt_diff, dt_u, dt_v, dt_w, dt_precipitation )
356	dt_3d = MIN( dt_3d, dt_max )
357	!
358	!-- In RANS mode, the time step must not increase by more than a factor of 2
359	IF ( rans_mode ) dt_3d = MIN( dt_3d, dt_max, 2.0_wp * old_dt )
360
361	!
362	!-- Remember the restricting time step criterion for later output.
363	IF ( MIN( dt_u, dt_v, dt_w ) < dt_diff ) THEN
364	timestep_reason = 'A'
365	ELSE
366	timestep_reason = 'D'
367	ENDIF
368
369	!
370	!-- Set flag if the time step becomes too small.
371	IF ( dt_3d < ( 0.00001_wp * dt_max ) ) THEN
372	stop_dt = .TRUE.
373
374	!
375	!-- Determine the maxima of the diffusion coefficients, including their
376	!-- grid index positions.
377	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, km, 'abs', &
378	0.0_wp, km_max, km_max_ijk )
379	CALL global_min_max( nzb, nzt+1, nysg, nyng, nxlg, nxrg, kh, 'abs', &
380	0.0_wp, kh_max, kh_max_ijk )
381
382	WRITE( message_string, * ) 'Time step has reached minimum limit.', &
383	'&dt = ', dt_3d, ' s Simulation is terminated.', &
384	'&old_dt = ', old_dt, ' s', &
385	'&dt_u = ', dt_u, ' s', &
386	'&dt_v = ', dt_v, ' s', &
387	'&dt_w = ', dt_w, ' s', &
388	'&dt_diff = ', dt_diff, ' s', &
389	'&u_max = ', u_max, ' m/s k=', u_max_ijk(1), &
390	' j=', u_max_ijk(2), ' i=', u_max_ijk(3), &
391	'&v_max = ', v_max, ' m/s k=', v_max_ijk(1), &
392	' j=', v_max_ijk(2), ' i=', v_max_ijk(3), &
393	'&w_max = ', w_max, ' m/s k=', w_max_ijk(1), &
394	' j=', w_max_ijk(2), ' i=', w_max_ijk(3), &
395	'&km_max = ', km_max, ' m2/s2 k=', km_max_ijk(1), &
396	' j=', km_max_ijk(2), ' i=', km_max_ijk(3), &
397	'&kh_max = ', kh_max, ' m2/s2 k=', kh_max_ijk(1), &
398	' j=', kh_max_ijk(2), ' i=', kh_max_ijk(3)
399	CALL message( 'timestep', 'PA0312', 0, 1, 0, 6, 0 )
400	!
401	!-- In case of coupled runs inform the remote model of the termination
402	!-- and its reason, provided the remote model has not already been
403	!-- informed of another termination reason (terminate_coupled > 0) before.
404	#if defined( __parallel )
405	IF ( coupling_mode /= 'uncoupled' .AND. terminate_coupled == 0 ) THEN
406	terminate_coupled = 2
407	IF ( myid == 0 ) THEN
408	CALL MPI_SENDRECV( &
409	terminate_coupled, 1, MPI_INTEGER, target_id, 0, &
410	terminate_coupled_remote, 1, MPI_INTEGER, target_id, 0, &
411	comm_inter, status, ierr )
412	ENDIF
413	CALL MPI_BCAST( terminate_coupled_remote, 1, MPI_INTEGER, 0, &
414	comm2d, ierr)
415	ENDIF
416	#endif
417	ENDIF
418
419	!
420	!-- In case of nested runs all parent/child processes have to terminate if
421	!-- one process has set the stop flag, i.e. they need to set the stop flag
422	!-- too.
423	IF ( nested_run ) THEN
424	stop_dt_local = stop_dt
425	#if defined( __parallel )
426	CALL MPI_ALLREDUCE( stop_dt_local, stop_dt, 1, MPI_LOGICAL, MPI_LOR, &
427	MPI_COMM_WORLD, ierr )
428	#endif
429	ENDIF
430
431	!
432	!-- Ensure a smooth value (two significant digits) of the timestep.
433	div = 1000.0_wp
434	DO WHILE ( dt_3d < div )
435	div = div / 10.0_wp
436	ENDDO
437	dt_3d = NINT( dt_3d * 100.0_wp / div ) * div / 100.0_wp
438
439	ENDIF
440
441	!
442	!-- Vertical nesting: coarse and fine grid timestep has to be identical
443	IF ( vnested ) CALL vnest_timestep_sync
444
445	CALL cpu_log( log_point(12), 'calculate_timestep', 'stop' )
446
447	END SUBROUTINE timestep

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