1 | SUBROUTINE FLOTT_GWD_RAN(NLON,NLEV,DTIME, pp, pn2, & |
---|
2 | tt,uu,vv,zustr,zvstr,d_t, d_u, d_v) |
---|
3 | |
---|
4 | !---------------------------------------------------------------------- |
---|
5 | ! Parametrization of the momentum flux deposition due to a discrete |
---|
6 | ! number of gravity waves. |
---|
7 | ! F. Lott (version 9: 16 February, 2012), reproduce v3 but with only |
---|
8 | ! two waves present at each time step |
---|
9 | ! LMDz model online version |
---|
10 | ! ADAPTED FOR VENUS |
---|
11 | !--------------------------------------------------------------------- |
---|
12 | |
---|
13 | use dimphy |
---|
14 | implicit none |
---|
15 | |
---|
16 | #include "YOEGWD.h" |
---|
17 | #include "YOMCST.h" |
---|
18 | |
---|
19 | ! 0. DECLARATIONS: |
---|
20 | |
---|
21 | ! 0.1 INPUTS |
---|
22 | INTEGER, intent(in):: NLON, NLEV |
---|
23 | REAL, intent(in):: DTIME ! Time step of the Physics |
---|
24 | REAL, intent(in):: pp(NLON, NLEV) ! Pressure at full levels |
---|
25 | ! VENUS ATTENTION: CP VARIABLE PN2 CALCULE EN AMONT DES PARAMETRISATIONS |
---|
26 | REAL, intent(in):: pn2(NLON,NLEV) ! N2 (BV^2) at 1/2 levels |
---|
27 | REAL, intent(in):: TT(NLON, NLEV) ! Temp at full levels |
---|
28 | |
---|
29 | REAL, intent(in):: UU(NLON, NLEV) , VV(NLON, NLEV) |
---|
30 | ! Hor winds at full levels |
---|
31 | |
---|
32 | ! 0.2 OUTPUTS |
---|
33 | REAL, intent(out):: zustr(NLON), zvstr(NLON) ! Surface Stresses |
---|
34 | REAL, intent(inout):: d_t(NLON, NLEV) ! Tendency on Temp. |
---|
35 | |
---|
36 | REAL, intent(inout):: d_u(NLON, NLEV), d_v(NLON, NLEV) |
---|
37 | ! Tendencies on winds |
---|
38 | |
---|
39 | ! O.3 INTERNAL ARRAYS |
---|
40 | |
---|
41 | INTEGER II, LL, IEQ |
---|
42 | |
---|
43 | ! 0.3.0 TIME SCALE OF THE LIFE CYCLE OF THE WAVES PARAMETERIZED |
---|
44 | |
---|
45 | REAL DELTAT |
---|
46 | |
---|
47 | ! 0.3.1 GRAVITY-WAVES SPECIFICATIONS |
---|
48 | |
---|
49 | !VENUS |
---|
50 | INTEGER, PARAMETER:: NK = 2, NP = 2, NO = 2, NW = NK * NP * NO |
---|
51 | !Online output: change NO |
---|
52 | ! INTEGER, PARAMETER:: NK = 1, NP = 2, NO = 11, NW = NK * NP * NO |
---|
53 | INTEGER JK, JP, JO, JW |
---|
54 | REAL KMIN, KMAX ! Min and Max horizontal wavenumbers |
---|
55 | REAL CMIN, CMAX ! Min and Max absolute ph. vel. |
---|
56 | REAL CPHA ! absolute PHASE VELOCITY frequency |
---|
57 | REAL ZK(NW, KLON) ! Horizontal wavenumber amplitude |
---|
58 | REAL ZP(NW) ! Horizontal wavenumber angle |
---|
59 | REAL ZO(NW, KLON) ! Absolute frequency ! |
---|
60 | |
---|
61 | ! Waves Intr. freq. at the 1/2 lev surrounding the full level |
---|
62 | REAL ZOM(NW, KLON), ZOP(NW, KLON) |
---|
63 | |
---|
64 | ! Wave vertical velocities at the 2 1/2 lev surrounding the full level |
---|
65 | REAL WWM(NW, KLON), WWP(NW, KLON) |
---|
66 | |
---|
67 | REAL RUW0(NW, KLON) ! Fluxes at launching level |
---|
68 | |
---|
69 | REAL RUWP(NW, KLON), RVWP(NW, KLON) |
---|
70 | ! Fluxes X and Y for each waves at 1/2 Levels |
---|
71 | |
---|
72 | INTEGER LAUNCH ! Launching altitude |
---|
73 | |
---|
74 | REAL RUWMAX,SAT ! saturation parameter |
---|
75 | REAL XLAUNCH ! Controle the launching altitude |
---|
76 | REAL RUW(KLON, KLEV + 1) ! Flux x at semi levels |
---|
77 | REAL RVW(KLON, KLEV + 1) ! Flux y at semi levels |
---|
78 | |
---|
79 | ! 0.3.2 PARAMETERS OF WAVES DISSIPATIONS |
---|
80 | |
---|
81 | REAL RDISS, ZOISEC ! COEFF DE DISSIPATION, SECURITY FOR INTRINSIC FREQ |
---|
82 | |
---|
83 | ! 0.3.3 BACKGROUND FLOW AT 1/2 LEVELS AND VERTICAL COORDINATE |
---|
84 | |
---|
85 | REAL H0bis(KLON, KLEV) ! Characteristic Height of the atmosphere |
---|
86 | REAL H0 ! Characteristic Height of the atmosphere |
---|
87 | REAL PR, TR ! Reference Pressure and Temperature |
---|
88 | |
---|
89 | REAL ZH(KLON, KLEV + 1) ! Log-pressure altitude (constant H0) |
---|
90 | REAL ZHbis(KLON, KLEV + 1) ! Log-pressure altitude (varying H) |
---|
91 | |
---|
92 | REAL UH(KLON, KLEV + 1), VH(KLON, KLEV + 1) ! Winds at 1/2 levels |
---|
93 | REAL PH(KLON, KLEV + 1) ! Pressure at 1/2 levels |
---|
94 | REAL PSEC ! Security to avoid division by 0 pressure |
---|
95 | REAL BV(KLON, KLEV + 1) ! Brunt Vaisala freq. (BVF) at 1/2 levels |
---|
96 | REAL BVSEC ! Security to avoid negative BVF |
---|
97 | |
---|
98 | ! COSMETICS TO DIAGNOSE EACH WAVES CONTRIBUTION. |
---|
99 | logical output |
---|
100 | data output/.false./ |
---|
101 | ! CAUTION ! IF output is .true. THEN change NO to 10 at least ! |
---|
102 | character*14 outform |
---|
103 | character*2 str2 |
---|
104 | |
---|
105 | ! ON CONSERVE LA MEMOIRE un certain temps AVEC UN SAVE |
---|
106 | real,save,allocatable :: d_u_sav(:,:),d_v_sav(:,:) |
---|
107 | LOGICAL firstcall |
---|
108 | SAVE firstcall |
---|
109 | DATA firstcall/.true./ |
---|
110 | |
---|
111 | REAL ALEAS |
---|
112 | EXTERNAL ALEAS |
---|
113 | |
---|
114 | !----------------------------------------------------------------- |
---|
115 | ! 1. INITIALISATIONS |
---|
116 | |
---|
117 | IF (firstcall) THEN |
---|
118 | allocate(d_u_sav(NLON,NLEV),d_v_sav(NLON,NLEV)) |
---|
119 | d_u_sav = 0. |
---|
120 | d_v_sav = 0. |
---|
121 | firstcall=.false. |
---|
122 | ENDIF |
---|
123 | |
---|
124 | ! 1.1 Basic parameter |
---|
125 | |
---|
126 | ! PARAMETERS CORRESPONDING TO V3: |
---|
127 | RUWMAX = 0.005 ! Max EP-Flux at Launch altitude |
---|
128 | SAT = 0.85 ! Saturation parameter: Sc in (12) |
---|
129 | RDISS = 10. ! Diffusion parameter |
---|
130 | |
---|
131 | DELTAT=24.*3600. ! Time scale of the waves (first introduced in 9b) |
---|
132 | |
---|
133 | KMIN = 1.E-6 ! Min horizontal wavenumber |
---|
134 | KMAX = 2.E-5 ! Max horizontal wavenumber |
---|
135 | !Online output: one value only |
---|
136 | if (output) then |
---|
137 | KMIN = 6.3E-6 |
---|
138 | KMAX = 6.3E-6 |
---|
139 | endif |
---|
140 | CMIN = 1. ! Min phase velocity |
---|
141 | CMAX = 61. ! Max phase speed velocity |
---|
142 | XLAUNCH=0.6 ! Parameter that control launching altitude |
---|
143 | |
---|
144 | PR = 9.2e6 ! Reference pressure ! VENUS!! |
---|
145 | TR = 240. ! Reference Temperature ! VENUS: cloud layer |
---|
146 | H0 = RD * TR / RG ! Characteristic vertical scale height |
---|
147 | |
---|
148 | BVSEC = 1.E-5 ! Security to avoid negative BVF |
---|
149 | PSEC = 1.E-8 ! Security to avoid division by 0 pressure |
---|
150 | ZOISEC = 1.E-8 ! Security FOR 0 INTRINSIC FREQ |
---|
151 | |
---|
152 | IF(DELTAT.LT.DTIME)THEN |
---|
153 | PRINT *,'GWD RANDO: DELTAT LT DTIME!' |
---|
154 | STOP |
---|
155 | ENDIF |
---|
156 | |
---|
157 | |
---|
158 | IF (NLEV < NW) THEN |
---|
159 | PRINT *, 'YOU WILL HAVE PROBLEM WITH RANDOM NUMBERS' |
---|
160 | PRINT *, 'FLOTT GWD STOP' |
---|
161 | STOP 1 |
---|
162 | ENDIF |
---|
163 | |
---|
164 | ! 1.2 WAVES CHARACTERISTICS CHOSEN RANDOMLY |
---|
165 | !------------------------------------------- |
---|
166 | |
---|
167 | ! The mod function of here a weird arguments |
---|
168 | ! are used to produce the waves characteristics |
---|
169 | ! in a stochastic way |
---|
170 | |
---|
171 | JW = 0 |
---|
172 | DO JP = 1, NP |
---|
173 | DO JK = 1, NK |
---|
174 | DO JO = 1, NO |
---|
175 | JW = JW + 1 |
---|
176 | ! Angle |
---|
177 | ZP(JW) = 2. * RPI * REAL(JP - 1) / REAL(NP) |
---|
178 | DO II = 1, KLON |
---|
179 | ! Horizontal wavenumber amplitude |
---|
180 | ! ZK(JW, II) = KMIN + (KMAX - KMIN) * MOD(TT(II, JW) * 100., 1.) |
---|
181 | ZK(JW, II) = KMIN + (KMAX - KMIN) * ALEAS(0.) |
---|
182 | ! Horizontal phase speed |
---|
183 | ! CPHA = CMIN + (CMAX - CMIN) * MOD(TT(II, JW)**2, 1.) |
---|
184 | CPHA = CMIN + (CMAX - CMIN) * ALEAS(0.) |
---|
185 | !Online output: linear |
---|
186 | if (output) CPHA = CMIN + (CMAX - CMIN) * (JO-1)/(NO-1) |
---|
187 | ! Intrinsic frequency |
---|
188 | ZO(JW, II) = CPHA * ZK(JW, II) |
---|
189 | ! Momentum flux at launch lev |
---|
190 | ! RUW0(JW, II) = RUWMAX / REAL(NW) & |
---|
191 | RUW0(JW, II) = RUWMAX & |
---|
192 | ! * MOD(100. * (UU(II, JW)**2 + VV(II, JW)**2), 1.) |
---|
193 | * ALEAS(0.) |
---|
194 | !Online output: fixed to max |
---|
195 | if (output) RUW0(JW, II) = RUWMAX |
---|
196 | ENDDO |
---|
197 | end DO |
---|
198 | end DO |
---|
199 | end DO |
---|
200 | |
---|
201 | ! 2. EVALUATION OF THE BACKGROUND FLOW AT SEMI-LEVELS |
---|
202 | !------------------------------------------------------------- |
---|
203 | |
---|
204 | IEQ = KLON / 2 |
---|
205 | !Online output |
---|
206 | if (output) OPEN(11,file="impact-gwno.dat") |
---|
207 | |
---|
208 | ! Pressure and Inv of pressure, Temperature / at 1/2 level |
---|
209 | DO LL = 2, KLEV |
---|
210 | PH(:, LL) = EXP((LOG(PP(:, LL)) + LOG(PP(:, LL - 1))) / 2.) |
---|
211 | end DO |
---|
212 | |
---|
213 | PH(:, KLEV + 1) = 0. |
---|
214 | PH(:, 1) = 2. * PP(:, 1) - PH(:, 2) |
---|
215 | |
---|
216 | ! Launching altitude |
---|
217 | |
---|
218 | DO LL = 1, NLEV |
---|
219 | IF (PH(IEQ, LL) / PH(IEQ, 1) > XLAUNCH) LAUNCH = LL |
---|
220 | ENDDO |
---|
221 | |
---|
222 | ! Log pressure vert. coordinate (altitude above surface) |
---|
223 | ZHbis(:,1) = 0. |
---|
224 | DO LL = 2, KLEV + 1 |
---|
225 | H0bis(:, LL-1) = RD * TT(:, LL-1) / RG |
---|
226 | ZHbis(:, LL) = ZHbis(:, LL-1) & |
---|
227 | + H0bis(:, LL-1)*(PH(:, LL-1)-PH(:,LL))/PP(:, LL-1) |
---|
228 | end DO |
---|
229 | ! Log pressure vert. coordinate |
---|
230 | DO LL = 1, KLEV + 1 |
---|
231 | ZH(:, LL) = H0 * LOG(PR / (PH(:, LL) + PSEC)) |
---|
232 | end DO |
---|
233 | |
---|
234 | |
---|
235 | ! Winds and BV frequency |
---|
236 | DO LL = 2, KLEV |
---|
237 | UH(:, LL) = 0.5 * (UU(:, LL) + UU(:, LL - 1)) ! Zonal wind |
---|
238 | VH(:, LL) = 0.5 * (VV(:, LL) + VV(:, LL - 1)) ! Meridional wind |
---|
239 | ! BVSEC: BV Frequency |
---|
240 | ! VENUS ATTENTION: CP VARIABLE PSTAB CALCULE EN AMONT DES PARAMETRISATIONS |
---|
241 | BV(:, LL) = MAX(BVSEC,SQRT(pn2(:,LL))) |
---|
242 | end DO |
---|
243 | BV(:, 1) = BV(:, 2) |
---|
244 | UH(:, 1) = 0. |
---|
245 | VH(:, 1) = 0. |
---|
246 | BV(:, KLEV + 1) = BV(:, KLEV) |
---|
247 | UH(:, KLEV + 1) = UU(:, KLEV) |
---|
248 | VH(:, KLEV + 1) = VV(:, KLEV) |
---|
249 | |
---|
250 | |
---|
251 | ! 3. COMPUTE THE FLUXES |
---|
252 | !-------------------------- |
---|
253 | |
---|
254 | ! 3.1 Vertical velocity at launching altitude to ensure |
---|
255 | ! the correct value to the imposed fluxes. |
---|
256 | ! |
---|
257 | DO JW = 1, NW |
---|
258 | |
---|
259 | ! Evaluate intrinsic frequency at launching altitude: |
---|
260 | ZOP(JW, :) = ZO(JW, :) & |
---|
261 | - ZK(JW, :) * COS(ZP(JW)) * UH(:, LAUNCH) & |
---|
262 | - ZK(JW, :) * SIN(ZP(JW)) * VH(:, LAUNCH) |
---|
263 | ! Vertical velocity at launch level, value to ensure the imposed |
---|
264 | ! mom flux: |
---|
265 | WWP(JW, :) = SQRT(ABS(ZOP(JW, :)) / MAX(BV(:, LAUNCH),BVSEC) & |
---|
266 | * RUW0(JW,:)) |
---|
267 | RUWP(JW, :) = COS(ZP(JW)) * SIGN(1., ZOP(JW, :)) * RUW0(JW, :) |
---|
268 | RVWP(JW, :) = SIN(ZP(JW)) * SIGN(1., ZOP(JW, :)) * RUW0(JW, :) |
---|
269 | |
---|
270 | end DO |
---|
271 | |
---|
272 | ! 3.2 Uniform values below the launching altitude |
---|
273 | |
---|
274 | DO LL = 1, LAUNCH |
---|
275 | RUW(:, LL) = 0 |
---|
276 | RVW(:, LL) = 0 |
---|
277 | DO JW = 1, NW |
---|
278 | RUW(:, LL) = RUW(:, LL) + RUWP(JW, :) |
---|
279 | RVW(:, LL) = RVW(:, LL) + RVWP(JW, :) |
---|
280 | end DO |
---|
281 | end DO |
---|
282 | |
---|
283 | ! 3.3 Loop over altitudes, with passage from one level to the |
---|
284 | ! next done by i) conserving the EP flux, ii) dissipating |
---|
285 | ! a little, iii) testing critical levels, and vi) testing |
---|
286 | ! the breaking. |
---|
287 | |
---|
288 | !Online output |
---|
289 | write(str2,'(i2)') NW+2 |
---|
290 | outform="("//str2//"(E12.4,1X))" |
---|
291 | if (output) WRITE(11,outform) ZH(IEQ, 1) / 1000., ZHbis(IEQ, 1) / 1000., & |
---|
292 | (ZO(JW, IEQ)/ZK(JW, IEQ)*COS(ZP(JW)), JW = 1, NW) |
---|
293 | |
---|
294 | DO LL = LAUNCH, KLEV - 1 |
---|
295 | |
---|
296 | |
---|
297 | ! W(KB)ARNING: ALL THE PHYSICS IS HERE (PASSAGE FROM ONE LEVEL |
---|
298 | ! TO THE NEXT) |
---|
299 | DO JW = 1, NW |
---|
300 | ZOM(JW, :) = ZOP(JW, :) |
---|
301 | WWM(JW, :) = WWP(JW, :) |
---|
302 | ! Intrinsic Frequency |
---|
303 | ZOP(JW, :) = ZO(JW, :) - ZK(JW, :) * COS(ZP(JW)) * UH(:, LL + 1) & |
---|
304 | - ZK(JW, :) * SIN(ZP(JW)) * VH(:, LL + 1) |
---|
305 | |
---|
306 | WWP(JW, :) = MIN( & |
---|
307 | ! No breaking (Eq.6) |
---|
308 | WWM(JW, :) & |
---|
309 | * SQRT(BV(:, LL ) / BV(:, LL+1) & |
---|
310 | * ABS(ZOP(JW, :)) / MAX(ABS(ZOM(JW, :)), ZOISEC)) & |
---|
311 | ! Dissipation (Eq. 8): |
---|
312 | * EXP(- RDISS * PR / (PH(:, LL + 1) + PH(:, LL)) & |
---|
313 | * ((BV(:, LL + 1) + BV(:, LL)) / 2.)**3 & |
---|
314 | / MAX(ABS(ZOP(JW, :) + ZOM(JW, :)) / 2., ZOISEC)**4 & |
---|
315 | * ZK(JW, :)**3 * (ZH(:, LL + 1) - ZH(:, LL))), & |
---|
316 | ! Critical levels (forced to zero if intrinsic |
---|
317 | ! frequency changes sign) |
---|
318 | MAX(0., SIGN(1., ZOP(JW, :) * ZOM(JW, :))) & |
---|
319 | ! Saturation (Eq. 12) |
---|
320 | * ZOP(JW, :)**2 / ZK(JW, :)/BV(:, LL+1) & |
---|
321 | * EXP(-ZH(:, LL + 1)/2./H0) * SAT) |
---|
322 | end DO |
---|
323 | |
---|
324 | ! END OF W(KB)ARNING |
---|
325 | ! Evaluate EP-flux from Eq. 7 and |
---|
326 | ! Give the right orientation to the stress |
---|
327 | |
---|
328 | DO JW = 1, NW |
---|
329 | RUWP(JW, :) = ZOP(JW, :)/MAX(ABS(ZOP(JW, :)), ZOISEC)**2 & |
---|
330 | *BV(:,LL+1)& |
---|
331 | * COS(ZP(JW)) * WWP(JW, :)**2 |
---|
332 | RVWP(JW, :) = ZOP(JW, :)/MAX(ABS(ZOP(JW, :)), ZOISEC)**2 & |
---|
333 | *BV(:,LL+1)& |
---|
334 | * SIN(ZP(JW)) * WWP(JW, :)**2 |
---|
335 | end DO |
---|
336 | ! |
---|
337 | RUW(:, LL + 1) = 0. |
---|
338 | RVW(:, LL + 1) = 0. |
---|
339 | |
---|
340 | DO JW = 1, NW |
---|
341 | RUW(:, LL + 1) = RUW(:, LL + 1) + RUWP(JW, :) |
---|
342 | RVW(:, LL + 1) = RVW(:, LL + 1) + RVWP(JW, :) |
---|
343 | end DO |
---|
344 | !Online output |
---|
345 | if (output) then |
---|
346 | do JW=1,NW |
---|
347 | if(RUWP(JW, IEQ).gt.0.) then |
---|
348 | RUWP(JW, IEQ) = max(RUWP(JW, IEQ), 1.e-99) |
---|
349 | else |
---|
350 | RUWP(JW, IEQ) = min(RUWP(JW, IEQ), -1.e-99) |
---|
351 | endif |
---|
352 | enddo |
---|
353 | WRITE(11,outform) ZH(IEQ, LL+1) / 1000., & |
---|
354 | ZHbis(IEQ, LL+1) / 1000., & |
---|
355 | (RUWP(JW, IEQ), JW = 1, NW) |
---|
356 | endif |
---|
357 | |
---|
358 | end DO |
---|
359 | |
---|
360 | !Online output |
---|
361 | if (output) then |
---|
362 | CLOSE(11) |
---|
363 | stop |
---|
364 | endif |
---|
365 | |
---|
366 | ! 4 CALCUL DES TENDANCES: |
---|
367 | !------------------------ |
---|
368 | |
---|
369 | ! 4.1 Rectification des flux au sommet et dans les basses couches: |
---|
370 | |
---|
371 | RUW(:, KLEV + 1) = 0. |
---|
372 | RVW(:, KLEV + 1) = 0. |
---|
373 | RUW(:, 1) = RUW(:, LAUNCH) |
---|
374 | RVW(:, 1) = RVW(:, LAUNCH) |
---|
375 | DO LL = 2, LAUNCH |
---|
376 | RUW(:, LL) = RUW(:, LL - 1) + (RUW(:, LAUNCH + 1) - RUW(:, 1)) * & |
---|
377 | (PH(:, LL) - PH(:, LL - 1)) / (PH(:, LAUNCH + 1) - PH(:, 1)) |
---|
378 | RVW(:, LL) = RVW(:, LL - 1) + (RVW(:, LAUNCH + 1) - RVW(:, 1)) * & |
---|
379 | (PH(:, LL) - PH(:, LL - 1)) / (PH(:, LAUNCH + 1) - PH(:, 1)) |
---|
380 | end DO |
---|
381 | |
---|
382 | ! AR-1 RECURSIVE FORMULA (13) IN VERSION 4 |
---|
383 | DO LL = 1, KLEV |
---|
384 | d_u(:, LL) = RG * (RUW(:, LL + 1) - RUW(:, LL)) & |
---|
385 | / (PH(:, LL + 1) - PH(:, LL)) * DTIME |
---|
386 | d_v(:, LL) = RG * (RVW(:, LL + 1) - RVW(:, LL)) & |
---|
387 | / (PH(:, LL + 1) - PH(:, LL)) * DTIME |
---|
388 | ENDDO |
---|
389 | d_t = 0. |
---|
390 | ! ON CONSERVE LA MEMOIRE un certain temps AVEC UN SAVE |
---|
391 | d_u = DTIME/DELTAT/REAL(NW) * d_u + (1.-DTIME/DELTAT) * d_u_sav |
---|
392 | d_v = DTIME/DELTAT/REAL(NW) * d_v + (1.-DTIME/DELTAT) * d_v_sav |
---|
393 | d_u_sav = d_u |
---|
394 | d_v_sav = d_v |
---|
395 | |
---|
396 | ! Cosmetic: evaluation of the cumulated stress |
---|
397 | |
---|
398 | ZUSTR(:) = 0. |
---|
399 | ZVSTR(:) = 0. |
---|
400 | DO LL = 1, KLEV |
---|
401 | ZUSTR(:) = ZUSTR(:) + D_U(:, LL) / RG * (PH(:, LL + 1) - PH(:, LL)) |
---|
402 | ZVSTR(:) = ZVSTR(:) + D_V(:, LL) / RG * (PH(:, LL + 1) - PH(:, LL)) |
---|
403 | ENDDO |
---|
404 | |
---|
405 | END SUBROUTINE FLOTT_GWD_RAN |
---|
406 | |
---|
407 | !=================================================================== |
---|
408 | !=================================================================== |
---|
409 | !=================================================================== |
---|
410 | !=================================================================== |
---|
411 | |
---|
412 | FUNCTION ALEAS (R) |
---|
413 | !***BEGIN PROLOGUE ALEAS |
---|
414 | !***PURPOSE Generate a uniformly distributed random number. |
---|
415 | !***LIBRARY SLATEC (FNLIB) |
---|
416 | !***CATEGORY L6A21 |
---|
417 | !***TYPE SINGLE PRECISION (ALEAS-S) |
---|
418 | !***KEYWORDS FNLIB, ALEAS NUMBER, SPECIAL FUNCTIONS, UNIFORM |
---|
419 | !***AUTHOR Fullerton, W., (LANL) |
---|
420 | !***DESCRIPTION |
---|
421 | ! |
---|
422 | ! This pseudo-random number generator is portable among a wide |
---|
423 | ! variety of computers. RAND(R) undoubtedly is not as good as many |
---|
424 | ! readily available installation dependent versions, and so this |
---|
425 | ! routine is not recommended for widespread usage. Its redeeming |
---|
426 | ! feature is that the exact same random numbers (to within final round- |
---|
427 | ! off error) can be generated from machine to machine. Thus, programs |
---|
428 | ! that make use of random numbers can be easily transported to and |
---|
429 | ! checked in a new environment. |
---|
430 | ! |
---|
431 | ! The random numbers are generated by the linear congruential |
---|
432 | ! method described, e.g., by Knuth in Seminumerical Methods (p.9), |
---|
433 | ! Addison-Wesley, 1969. Given the I-th number of a pseudo-random |
---|
434 | ! sequence, the I+1 -st number is generated from |
---|
435 | ! X(I+1) = (A*X(I) + C) MOD M, |
---|
436 | ! where here M = 2**22 = 4194304, C = 1731 and several suitable values |
---|
437 | ! of the multiplier A are discussed below. Both the multiplier A and |
---|
438 | ! random number X are represented in double precision as two 11-bit |
---|
439 | ! words. The constants are chosen so that the period is the maximum |
---|
440 | ! possible, 4194304. |
---|
441 | ! |
---|
442 | ! In order that the same numbers be generated from machine to |
---|
443 | ! machine, it is necessary that 23-bit integers be reducible modulo |
---|
444 | ! 2**11 exactly, that 23-bit integers be added exactly, and that 11-bit |
---|
445 | ! integers be multiplied exactly. Furthermore, if the restart option |
---|
446 | ! is used (where R is between 0 and 1), then the product R*2**22 = |
---|
447 | ! R*4194304 must be correct to the nearest integer. |
---|
448 | ! |
---|
449 | ! The first four random numbers should be .0004127026, |
---|
450 | ! .6750836372, .1614754200, and .9086198807. The tenth random number |
---|
451 | ! is .5527787209, and the hundredth is .3600893021 . The thousandth |
---|
452 | ! number should be .2176990509 . |
---|
453 | ! |
---|
454 | ! In order to generate several effectively independent sequences |
---|
455 | ! with the same generator, it is necessary to know the random number |
---|
456 | ! for several widely spaced calls. The I-th random number times 2**22, |
---|
457 | ! where I=K*P/8 and P is the period of the sequence (P = 2**22), is |
---|
458 | ! still of the form L*P/8. In particular we find the I-th random |
---|
459 | ! number multiplied by 2**22 is given by |
---|
460 | ! I = 0 1*P/8 2*P/8 3*P/8 4*P/8 5*P/8 6*P/8 7*P/8 8*P/8 |
---|
461 | ! RAND= 0 5*P/8 2*P/8 7*P/8 4*P/8 1*P/8 6*P/8 3*P/8 0 |
---|
462 | ! Thus the 4*P/8 = 2097152 random number is 2097152/2**22. |
---|
463 | ! |
---|
464 | ! Several multipliers have been subjected to the spectral test |
---|
465 | ! (see Knuth, p. 82). Four suitable multipliers roughly in order of |
---|
466 | ! goodness according to the spectral test are |
---|
467 | ! 3146757 = 1536*2048 + 1029 = 2**21 + 2**20 + 2**10 + 5 |
---|
468 | ! 2098181 = 1024*2048 + 1029 = 2**21 + 2**10 + 5 |
---|
469 | ! 3146245 = 1536*2048 + 517 = 2**21 + 2**20 + 2**9 + 5 |
---|
470 | ! 2776669 = 1355*2048 + 1629 = 5**9 + 7**7 + 1 |
---|
471 | ! |
---|
472 | ! In the table below LOG10(NU(I)) gives roughly the number of |
---|
473 | ! random decimal digits in the random numbers considered I at a time. |
---|
474 | ! C is the primary measure of goodness. In both cases bigger is better. |
---|
475 | ! |
---|
476 | ! LOG10 NU(I) C(I) |
---|
477 | ! A I=2 I=3 I=4 I=5 I=2 I=3 I=4 I=5 |
---|
478 | ! |
---|
479 | ! 3146757 3.3 2.0 1.6 1.3 3.1 1.3 4.6 2.6 |
---|
480 | ! 2098181 3.3 2.0 1.6 1.2 3.2 1.3 4.6 1.7 |
---|
481 | ! 3146245 3.3 2.2 1.5 1.1 3.2 4.2 1.1 0.4 |
---|
482 | ! 2776669 3.3 2.1 1.6 1.3 2.5 2.0 1.9 2.6 |
---|
483 | ! Best |
---|
484 | ! Possible 3.3 2.3 1.7 1.4 3.6 5.9 9.7 14.9 |
---|
485 | ! |
---|
486 | ! Input Argument -- |
---|
487 | ! R If R=0., the next random number of the sequence is generated. |
---|
488 | ! If R .LT. 0., the last generated number will be returned for |
---|
489 | ! possible use in a restart procedure. |
---|
490 | ! If R .GT. 0., the sequence of random numbers will start with |
---|
491 | ! the seed R mod 1. This seed is also returned as the value of |
---|
492 | ! RAND provided the arithmetic is done exactly. |
---|
493 | ! |
---|
494 | ! Output Value -- |
---|
495 | ! RAND a pseudo-random number between 0. and 1. |
---|
496 | ! |
---|
497 | !***REFERENCES (NONE) |
---|
498 | !***ROUTINES CALLED (NONE) |
---|
499 | !***REVISION HISTORY (YYMMDD) |
---|
500 | ! 770401 DATE WRITTEN |
---|
501 | ! 890531 Changed all specific intrinsics to generic. (WRB) |
---|
502 | ! 890531 REVISION DATE from Version 3.2 |
---|
503 | ! 891214 Prologue converted to Version 4.0 format. (BAB) |
---|
504 | !***END PROLOGUE RAND |
---|
505 | SAVE IA1, IA0, IA1MA0, IC, IX1, IX0 |
---|
506 | DATA IA1, IA0, IA1MA0 /1536, 1029, 507/ |
---|
507 | DATA IC /1731/ |
---|
508 | DATA IX1, IX0 /0, 0/ |
---|
509 | !***FIRST EXECUTABLE STATEMENT RAND |
---|
510 | ! |
---|
511 | ! A*X = 2**22*IA1*IX1 + 2**11*(IA1*IX1 + (IA1-IA0)*(IX0-IX1) |
---|
512 | ! + IA0*IX0) + IA0*IX0 |
---|
513 | ! |
---|
514 | IF (R.EQ.0.) THEN |
---|
515 | IY0 = IA0*IX0 |
---|
516 | IY1 = IA1*IX1 + IA1MA0*(IX0-IX1) + IY0 |
---|
517 | IY0 = IY0 + IC |
---|
518 | IX0 = MOD (IY0, 2048) |
---|
519 | IY1 = IY1 + (IY0-IX0)/2048 |
---|
520 | IX1 = MOD (IY1, 2048) |
---|
521 | ENDIF |
---|
522 | |
---|
523 | IF (R.GT.0.) THEN |
---|
524 | IX1 = MOD(R,1.)*4194304. + 0.5 |
---|
525 | IX0 = MOD (IX1, 2048) |
---|
526 | IX1 = (IX1-IX0)/2048 |
---|
527 | ENDIF |
---|
528 | |
---|
529 | ALEAS = IX1*2048 + IX0 |
---|
530 | ALEAS = ALEAS / 4194304. |
---|
531 | RETURN |
---|
532 | |
---|
533 | END |
---|
534 | |
---|
535 | |
---|