1 | !> @file diffusion_w.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 1997-2020 Leibniz Universitaet Hannover |
---|
18 | !------------------------------------------------------------------------------! |
---|
19 | ! |
---|
20 | ! Current revisions: |
---|
21 | ! ----------------- |
---|
22 | ! |
---|
23 | ! |
---|
24 | ! Former revisions: |
---|
25 | ! ----------------- |
---|
26 | ! $Id: diffusion_w.f90 4360 2020-01-07 11:25:50Z suehring $ |
---|
27 | ! Introduction of wall_flags_total_0, which currently sets bits based on static |
---|
28 | ! topography information used in wall_flags_static_0 |
---|
29 | ! |
---|
30 | ! 4329 2019-12-10 15:46:36Z motisi |
---|
31 | ! Renamed wall_flags_0 to wall_flags_static_0 |
---|
32 | ! |
---|
33 | ! 4182 2019-08-22 15:20:23Z scharf |
---|
34 | ! Corrected "Former revisions" section |
---|
35 | ! |
---|
36 | ! 3655 2019-01-07 16:51:22Z knoop |
---|
37 | ! OpenACC port for SPEC |
---|
38 | ! |
---|
39 | ! Revision 1.1 1997/09/12 06:24:11 raasch |
---|
40 | ! Initial revision |
---|
41 | ! |
---|
42 | ! |
---|
43 | ! Description: |
---|
44 | ! ------------ |
---|
45 | !> Diffusion term of the w-component |
---|
46 | !------------------------------------------------------------------------------! |
---|
47 | MODULE diffusion_w_mod |
---|
48 | |
---|
49 | |
---|
50 | PRIVATE |
---|
51 | PUBLIC diffusion_w |
---|
52 | |
---|
53 | INTERFACE diffusion_w |
---|
54 | MODULE PROCEDURE diffusion_w |
---|
55 | MODULE PROCEDURE diffusion_w_ij |
---|
56 | END INTERFACE diffusion_w |
---|
57 | |
---|
58 | CONTAINS |
---|
59 | |
---|
60 | |
---|
61 | !------------------------------------------------------------------------------! |
---|
62 | ! Description: |
---|
63 | ! ------------ |
---|
64 | !> Call for all grid points |
---|
65 | !------------------------------------------------------------------------------! |
---|
66 | SUBROUTINE diffusion_w |
---|
67 | |
---|
68 | USE arrays_3d, & |
---|
69 | ONLY : ddzu, ddzw, km, tend, u, v, w, drho_air_zw, rho_air |
---|
70 | |
---|
71 | USE grid_variables, & |
---|
72 | ONLY : ddx, ddy |
---|
73 | |
---|
74 | USE indices, & |
---|
75 | ONLY : nxl, nxr, nyn, nys, nzb, nzt, wall_flags_total_0 |
---|
76 | |
---|
77 | USE kinds |
---|
78 | |
---|
79 | USE surface_mod, & |
---|
80 | ONLY : surf_def_v, surf_lsm_v, surf_usm_v |
---|
81 | |
---|
82 | IMPLICIT NONE |
---|
83 | |
---|
84 | INTEGER(iwp) :: i !< running index x direction |
---|
85 | INTEGER(iwp) :: j !< running index y direction |
---|
86 | INTEGER(iwp) :: k !< running index z direction |
---|
87 | INTEGER(iwp) :: l !< running index of surface type, south- or north-facing wall |
---|
88 | INTEGER(iwp) :: m !< running index surface elements |
---|
89 | INTEGER(iwp) :: surf_e !< End index of surface elements at (j,i)-gridpoint |
---|
90 | INTEGER(iwp) :: surf_s !< Start index of surface elements at (j,i)-gridpoint |
---|
91 | |
---|
92 | REAL(wp) :: flag !< flag to mask topography grid points |
---|
93 | REAL(wp) :: kmxm !< diffusion coefficient on leftward side of the w-gridbox - interpolated onto xu-y grid |
---|
94 | REAL(wp) :: kmxp !<diffusion coefficient on rightward side of the w-gridbox - interpolated onto xu-y grid |
---|
95 | REAL(wp) :: kmym !< diffusion coefficient on southward side of the w-gridbox - interpolated onto x-yv grid |
---|
96 | REAL(wp) :: kmyp !< diffusion coefficient on northward side of the w-gridbox - interpolated onto x-yv grid |
---|
97 | REAL(wp) :: mask_west !< flag to mask vertical wall west of the grid point |
---|
98 | REAL(wp) :: mask_east !< flag to mask vertical wall east of the grid point |
---|
99 | REAL(wp) :: mask_south !< flag to mask vertical wall south of the grid point |
---|
100 | REAL(wp) :: mask_north !< flag to mask vertical wall north of the grid point |
---|
101 | |
---|
102 | |
---|
103 | |
---|
104 | !$ACC PARALLEL LOOP COLLAPSE(2) PRIVATE(i, j, k, l, m) & |
---|
105 | !$ACC PRIVATE(surf_e, surf_s, flag, kmxm, kmxp, kmym, kmyp) & |
---|
106 | !$ACC PRIVATE(mask_west, mask_east, mask_south, mask_north) & |
---|
107 | !$ACC PRESENT(wall_flags_total_0, km) & |
---|
108 | !$ACC PRESENT(u, v, w) & |
---|
109 | !$ACC PRESENT(ddzu, ddzw, rho_air, drho_air_zw) & |
---|
110 | !$ACC PRESENT(surf_def_v(0:3)) & |
---|
111 | !$ACC PRESENT(surf_lsm_v(0:3)) & |
---|
112 | !$ACC PRESENT(surf_usm_v(0:3)) & |
---|
113 | !$ACC PRESENT(tend) |
---|
114 | DO i = nxl, nxr |
---|
115 | DO j = nys, nyn |
---|
116 | DO k = nzb+1, nzt-1 |
---|
117 | ! |
---|
118 | !-- Predetermine flag to mask topography and wall-bounded grid points. |
---|
119 | flag = MERGE( 1.0_wp, 0.0_wp, & |
---|
120 | BTEST( wall_flags_total_0(k,j,i), 3 ) ) |
---|
121 | mask_east = MERGE( 1.0_wp, 0.0_wp, & |
---|
122 | BTEST( wall_flags_total_0(k,j,i+1), 3 ) ) |
---|
123 | mask_west = MERGE( 1.0_wp, 0.0_wp, & |
---|
124 | BTEST( wall_flags_total_0(k,j,i-1), 3 ) ) |
---|
125 | mask_south = MERGE( 1.0_wp, 0.0_wp, & |
---|
126 | BTEST( wall_flags_total_0(k,j-1,i), 3 ) ) |
---|
127 | mask_north = MERGE( 1.0_wp, 0.0_wp, & |
---|
128 | BTEST( wall_flags_total_0(k,j+1,i), 3 ) ) |
---|
129 | ! |
---|
130 | !-- Interpolate eddy diffusivities on staggered gridpoints |
---|
131 | kmxp = 0.25_wp * ( km(k,j,i) + km(k,j,i+1) + & |
---|
132 | km(k+1,j,i) + km(k+1,j,i+1) ) |
---|
133 | kmxm = 0.25_wp * ( km(k,j,i) + km(k,j,i-1) + & |
---|
134 | km(k+1,j,i) + km(k+1,j,i-1) ) |
---|
135 | kmyp = 0.25_wp * ( km(k,j,i) + km(k+1,j,i) + & |
---|
136 | km(k,j+1,i) + km(k+1,j+1,i) ) |
---|
137 | kmym = 0.25_wp * ( km(k,j,i) + km(k+1,j,i) + & |
---|
138 | km(k,j-1,i) + km(k+1,j-1,i) ) |
---|
139 | |
---|
140 | tend(k,j,i) = tend(k,j,i) & |
---|
141 | + ( mask_east * kmxp * ( & |
---|
142 | ( w(k,j,i+1) - w(k,j,i) ) * ddx & |
---|
143 | + ( u(k+1,j,i+1) - u(k,j,i+1) ) * ddzu(k+1) & |
---|
144 | ) & |
---|
145 | - mask_west * kmxm * ( & |
---|
146 | ( w(k,j,i) - w(k,j,i-1) ) * ddx & |
---|
147 | + ( u(k+1,j,i) - u(k,j,i) ) * ddzu(k+1) & |
---|
148 | ) & |
---|
149 | ) * ddx * flag & |
---|
150 | + ( mask_north * kmyp * ( & |
---|
151 | ( w(k,j+1,i) - w(k,j,i) ) * ddy & |
---|
152 | + ( v(k+1,j+1,i) - v(k,j+1,i) ) * ddzu(k+1) & |
---|
153 | ) & |
---|
154 | - mask_south * kmym * ( & |
---|
155 | ( w(k,j,i) - w(k,j-1,i) ) * ddy & |
---|
156 | + ( v(k+1,j,i) - v(k,j,i) ) * ddzu(k+1) & |
---|
157 | ) & |
---|
158 | ) * ddy * flag & |
---|
159 | + 2.0_wp * ( & |
---|
160 | km(k+1,j,i) * ( w(k+1,j,i) - w(k,j,i) ) * ddzw(k+1) & |
---|
161 | * rho_air(k+1) & |
---|
162 | - km(k,j,i) * ( w(k,j,i) - w(k-1,j,i) ) * ddzw(k) & |
---|
163 | * rho_air(k) & |
---|
164 | ) * ddzu(k+1) * drho_air_zw(k) * flag |
---|
165 | ENDDO |
---|
166 | |
---|
167 | ! |
---|
168 | !-- Add horizontal momentum flux v'w' at north- (l=0) and south-facing (l=1) |
---|
169 | !-- surfaces. Note, in the the flat case, loops won't be entered as |
---|
170 | !-- start_index > end_index. Furtermore, note, no vertical natural surfaces |
---|
171 | !-- so far. |
---|
172 | !-- Default-type surfaces |
---|
173 | DO l = 0, 1 |
---|
174 | surf_s = surf_def_v(l)%start_index(j,i) |
---|
175 | surf_e = surf_def_v(l)%end_index(j,i) |
---|
176 | DO m = surf_s, surf_e |
---|
177 | k = surf_def_v(l)%k(m) |
---|
178 | tend(k,j,i) = tend(k,j,i) + & |
---|
179 | surf_def_v(l)%mom_flux_w(m) * ddy |
---|
180 | ENDDO |
---|
181 | ENDDO |
---|
182 | ! |
---|
183 | !-- Natural-type surfaces |
---|
184 | DO l = 0, 1 |
---|
185 | surf_s = surf_lsm_v(l)%start_index(j,i) |
---|
186 | surf_e = surf_lsm_v(l)%end_index(j,i) |
---|
187 | DO m = surf_s, surf_e |
---|
188 | k = surf_lsm_v(l)%k(m) |
---|
189 | tend(k,j,i) = tend(k,j,i) + & |
---|
190 | surf_lsm_v(l)%mom_flux_w(m) * ddy |
---|
191 | ENDDO |
---|
192 | ENDDO |
---|
193 | ! |
---|
194 | !-- Urban-type surfaces |
---|
195 | DO l = 0, 1 |
---|
196 | surf_s = surf_usm_v(l)%start_index(j,i) |
---|
197 | surf_e = surf_usm_v(l)%end_index(j,i) |
---|
198 | DO m = surf_s, surf_e |
---|
199 | k = surf_usm_v(l)%k(m) |
---|
200 | tend(k,j,i) = tend(k,j,i) + & |
---|
201 | surf_usm_v(l)%mom_flux_w(m) * ddy |
---|
202 | ENDDO |
---|
203 | ENDDO |
---|
204 | ! |
---|
205 | !-- Add horizontal momentum flux u'w' at east- (l=2) and west-facing (l=3) |
---|
206 | !-- surface. |
---|
207 | !-- Default-type surfaces |
---|
208 | DO l = 2, 3 |
---|
209 | surf_s = surf_def_v(l)%start_index(j,i) |
---|
210 | surf_e = surf_def_v(l)%end_index(j,i) |
---|
211 | DO m = surf_s, surf_e |
---|
212 | k = surf_def_v(l)%k(m) |
---|
213 | tend(k,j,i) = tend(k,j,i) + & |
---|
214 | surf_def_v(l)%mom_flux_w(m) * ddx |
---|
215 | ENDDO |
---|
216 | ENDDO |
---|
217 | ! |
---|
218 | !-- Natural-type surfaces |
---|
219 | DO l = 2, 3 |
---|
220 | surf_s = surf_lsm_v(l)%start_index(j,i) |
---|
221 | surf_e = surf_lsm_v(l)%end_index(j,i) |
---|
222 | DO m = surf_s, surf_e |
---|
223 | k = surf_lsm_v(l)%k(m) |
---|
224 | tend(k,j,i) = tend(k,j,i) + & |
---|
225 | surf_lsm_v(l)%mom_flux_w(m) * ddx |
---|
226 | ENDDO |
---|
227 | ENDDO |
---|
228 | ! |
---|
229 | !-- Urban-type surfaces |
---|
230 | DO l = 2, 3 |
---|
231 | surf_s = surf_usm_v(l)%start_index(j,i) |
---|
232 | surf_e = surf_usm_v(l)%end_index(j,i) |
---|
233 | DO m = surf_s, surf_e |
---|
234 | k = surf_usm_v(l)%k(m) |
---|
235 | tend(k,j,i) = tend(k,j,i) + & |
---|
236 | surf_usm_v(l)%mom_flux_w(m) * ddx |
---|
237 | ENDDO |
---|
238 | ENDDO |
---|
239 | |
---|
240 | ENDDO |
---|
241 | ENDDO |
---|
242 | |
---|
243 | END SUBROUTINE diffusion_w |
---|
244 | |
---|
245 | |
---|
246 | !------------------------------------------------------------------------------! |
---|
247 | ! Description: |
---|
248 | ! ------------ |
---|
249 | !> Call for grid point i,j |
---|
250 | !------------------------------------------------------------------------------! |
---|
251 | SUBROUTINE diffusion_w_ij( i, j ) |
---|
252 | |
---|
253 | USE arrays_3d, & |
---|
254 | ONLY : ddzu, ddzw, km, tend, u, v, w, drho_air_zw, rho_air |
---|
255 | |
---|
256 | USE grid_variables, & |
---|
257 | ONLY : ddx, ddy |
---|
258 | |
---|
259 | USE indices, & |
---|
260 | ONLY : nzb, nzt, wall_flags_total_0 |
---|
261 | |
---|
262 | USE kinds |
---|
263 | |
---|
264 | USE surface_mod, & |
---|
265 | ONLY : surf_def_v, surf_lsm_v, surf_usm_v |
---|
266 | |
---|
267 | IMPLICIT NONE |
---|
268 | |
---|
269 | |
---|
270 | INTEGER(iwp) :: i !< running index x direction |
---|
271 | INTEGER(iwp) :: j !< running index y direction |
---|
272 | INTEGER(iwp) :: k !< running index z direction |
---|
273 | INTEGER(iwp) :: l !< running index of surface type, south- or north-facing wall |
---|
274 | INTEGER(iwp) :: m !< running index surface elements |
---|
275 | INTEGER(iwp) :: surf_e !< End index of surface elements at (j,i)-gridpoint |
---|
276 | INTEGER(iwp) :: surf_s !< Start index of surface elements at (j,i)-gridpoint |
---|
277 | |
---|
278 | REAL(wp) :: flag !< flag to mask topography grid points |
---|
279 | REAL(wp) :: kmxm !< diffusion coefficient on leftward side of the w-gridbox - interpolated onto xu-y grid |
---|
280 | REAL(wp) :: kmxp !< diffusion coefficient on rightward side of the w-gridbox - interpolated onto xu-y grid |
---|
281 | REAL(wp) :: kmym !< diffusion coefficient on southward side of the w-gridbox - interpolated onto x-yv grid |
---|
282 | REAL(wp) :: kmyp !< diffusion coefficient on northward side of the w-gridbox - interpolated onto x-yv grid |
---|
283 | REAL(wp) :: mask_west !< flag to mask vertical wall west of the grid point |
---|
284 | REAL(wp) :: mask_east !< flag to mask vertical wall east of the grid point |
---|
285 | REAL(wp) :: mask_south !< flag to mask vertical wall south of the grid point |
---|
286 | REAL(wp) :: mask_north !< flag to mask vertical wall north of the grid point |
---|
287 | |
---|
288 | |
---|
289 | DO k = nzb+1, nzt-1 |
---|
290 | ! |
---|
291 | !-- Predetermine flag to mask topography and wall-bounded grid points. |
---|
292 | flag = MERGE( 1.0_wp, 0.0_wp, BTEST( wall_flags_total_0(k,j,i), 3 ) ) |
---|
293 | mask_east = MERGE( 1.0_wp, 0.0_wp, BTEST( wall_flags_total_0(k,j,i+1), 3 ) ) |
---|
294 | mask_west = MERGE( 1.0_wp, 0.0_wp, BTEST( wall_flags_total_0(k,j,i-1), 3 ) ) |
---|
295 | mask_south = MERGE( 1.0_wp, 0.0_wp, BTEST( wall_flags_total_0(k,j-1,i), 3 ) ) |
---|
296 | mask_north = MERGE( 1.0_wp, 0.0_wp, BTEST( wall_flags_total_0(k,j+1,i), 3 ) ) |
---|
297 | ! |
---|
298 | !-- Interpolate eddy diffusivities on staggered gridpoints |
---|
299 | kmxp = 0.25_wp * ( km(k,j,i)+km(k,j,i+1)+km(k+1,j,i)+km(k+1,j,i+1) ) |
---|
300 | kmxm = 0.25_wp * ( km(k,j,i)+km(k,j,i-1)+km(k+1,j,i)+km(k+1,j,i-1) ) |
---|
301 | kmyp = 0.25_wp * ( km(k,j,i)+km(k+1,j,i)+km(k,j+1,i)+km(k+1,j+1,i) ) |
---|
302 | kmym = 0.25_wp * ( km(k,j,i)+km(k+1,j,i)+km(k,j-1,i)+km(k+1,j-1,i) ) |
---|
303 | |
---|
304 | tend(k,j,i) = tend(k,j,i) & |
---|
305 | + ( mask_east * kmxp * ( & |
---|
306 | ( w(k,j,i+1) - w(k,j,i) ) * ddx & |
---|
307 | + ( u(k+1,j,i+1) - u(k,j,i+1) ) * ddzu(k+1) & |
---|
308 | ) & |
---|
309 | - mask_west * kmxm * ( & |
---|
310 | ( w(k,j,i) - w(k,j,i-1) ) * ddx & |
---|
311 | + ( u(k+1,j,i) - u(k,j,i) ) * ddzu(k+1) & |
---|
312 | ) & |
---|
313 | ) * ddx * flag & |
---|
314 | + ( mask_north * kmyp * ( & |
---|
315 | ( w(k,j+1,i) - w(k,j,i) ) * ddy & |
---|
316 | + ( v(k+1,j+1,i) - v(k,j+1,i) ) * ddzu(k+1) & |
---|
317 | ) & |
---|
318 | - mask_south * kmym * ( & |
---|
319 | ( w(k,j,i) - w(k,j-1,i) ) * ddy & |
---|
320 | + ( v(k+1,j,i) - v(k,j,i) ) * ddzu(k+1) & |
---|
321 | ) & |
---|
322 | ) * ddy * flag & |
---|
323 | + 2.0_wp * ( & |
---|
324 | km(k+1,j,i) * ( w(k+1,j,i) - w(k,j,i) ) * ddzw(k+1) & |
---|
325 | * rho_air(k+1) & |
---|
326 | - km(k,j,i) * ( w(k,j,i) - w(k-1,j,i) ) * ddzw(k) & |
---|
327 | * rho_air(k) & |
---|
328 | ) * ddzu(k+1) * drho_air_zw(k) * flag |
---|
329 | ENDDO |
---|
330 | ! |
---|
331 | !-- Add horizontal momentum flux v'w' at north- (l=0) and south-facing (l=1) |
---|
332 | !-- surfaces. Note, in the the flat case, loops won't be entered as |
---|
333 | !-- start_index > end_index. Furtermore, note, no vertical natural surfaces |
---|
334 | !-- so far. |
---|
335 | !-- Default-type surfaces |
---|
336 | DO l = 0, 1 |
---|
337 | surf_s = surf_def_v(l)%start_index(j,i) |
---|
338 | surf_e = surf_def_v(l)%end_index(j,i) |
---|
339 | DO m = surf_s, surf_e |
---|
340 | k = surf_def_v(l)%k(m) |
---|
341 | tend(k,j,i) = tend(k,j,i) + & |
---|
342 | surf_def_v(l)%mom_flux_w(m) * ddy |
---|
343 | ENDDO |
---|
344 | ENDDO |
---|
345 | ! |
---|
346 | !-- Natural-type surfaces |
---|
347 | DO l = 0, 1 |
---|
348 | surf_s = surf_lsm_v(l)%start_index(j,i) |
---|
349 | surf_e = surf_lsm_v(l)%end_index(j,i) |
---|
350 | DO m = surf_s, surf_e |
---|
351 | k = surf_lsm_v(l)%k(m) |
---|
352 | tend(k,j,i) = tend(k,j,i) + & |
---|
353 | surf_lsm_v(l)%mom_flux_w(m) * ddy |
---|
354 | ENDDO |
---|
355 | ENDDO |
---|
356 | ! |
---|
357 | !-- Urban-type surfaces |
---|
358 | DO l = 0, 1 |
---|
359 | surf_s = surf_usm_v(l)%start_index(j,i) |
---|
360 | surf_e = surf_usm_v(l)%end_index(j,i) |
---|
361 | DO m = surf_s, surf_e |
---|
362 | k = surf_usm_v(l)%k(m) |
---|
363 | tend(k,j,i) = tend(k,j,i) + & |
---|
364 | surf_usm_v(l)%mom_flux_w(m) * ddy |
---|
365 | ENDDO |
---|
366 | ENDDO |
---|
367 | ! |
---|
368 | !-- Add horizontal momentum flux u'w' at east- (l=2) and west-facing (l=3) |
---|
369 | !-- surfaces. |
---|
370 | !-- Default-type surfaces |
---|
371 | DO l = 2, 3 |
---|
372 | surf_s = surf_def_v(l)%start_index(j,i) |
---|
373 | surf_e = surf_def_v(l)%end_index(j,i) |
---|
374 | DO m = surf_s, surf_e |
---|
375 | k = surf_def_v(l)%k(m) |
---|
376 | tend(k,j,i) = tend(k,j,i) + & |
---|
377 | surf_def_v(l)%mom_flux_w(m) * ddx |
---|
378 | ENDDO |
---|
379 | ENDDO |
---|
380 | ! |
---|
381 | !-- Natural-type surfaces |
---|
382 | DO l = 2, 3 |
---|
383 | surf_s = surf_lsm_v(l)%start_index(j,i) |
---|
384 | surf_e = surf_lsm_v(l)%end_index(j,i) |
---|
385 | DO m = surf_s, surf_e |
---|
386 | k = surf_lsm_v(l)%k(m) |
---|
387 | tend(k,j,i) = tend(k,j,i) + & |
---|
388 | surf_lsm_v(l)%mom_flux_w(m) * ddx |
---|
389 | ENDDO |
---|
390 | ENDDO |
---|
391 | ! |
---|
392 | !-- Urban-type surfaces |
---|
393 | DO l = 2, 3 |
---|
394 | surf_s = surf_usm_v(l)%start_index(j,i) |
---|
395 | surf_e = surf_usm_v(l)%end_index(j,i) |
---|
396 | DO m = surf_s, surf_e |
---|
397 | k = surf_usm_v(l)%k(m) |
---|
398 | tend(k,j,i) = tend(k,j,i) + & |
---|
399 | surf_usm_v(l)%mom_flux_w(m) * ddx |
---|
400 | ENDDO |
---|
401 | ENDDO |
---|
402 | |
---|
403 | |
---|
404 | END SUBROUTINE diffusion_w_ij |
---|
405 | |
---|
406 | END MODULE diffusion_w_mod |
---|