Changeset 4545 for palm/trunk/SOURCE/random_generator_parallel_mod.f90

Timestamp:

May 22, 2020 1:17:57 PM (4 years ago)

Author:

schwenkel

Message:

Add gaussian random number generator to parallel random generator and using parallel random number in lpm

File:

• palm/trunk/SOURCE/random_generator_parallel_mod.f90 (modified) (5 diffs)

palm/trunk/SOURCE/random_generator_parallel_mod.f90

@@ -25 +25 @@
 ! -----------------
 ! $Id$
+! Add generator (using parallel mode) returning gaussian distributed random
+! number
+! 
+! 4438 2020-03-03 20:49:28Z raasch
 ! - Rename variables to avoid confusion with subdomain grid indices
 ! - Some formatting adjustments
@@ -45 +49 @@
 !> ran_parallel returns a uniform random deviate between 0.0 and 1.0 
 !> (exclusive of the end point values).
+!> Moreover, it contains a routine returning a normally distributed random number
+!> with mean zero and unity standard deviation.
 !> Additionally it provides the generator with five integer for use as initial state space.
 !> The first tree integers (iran, jran, kran) are maintained as non negative values, 
@@ -95 +101 @@
    END INTERFACE
 
+   INTERFACE random_number_parallel_gauss
+      MODULE PROCEDURE gasdev_s
+   END INTERFACE
+
    INTERFACE random_seed_parallel
       MODULE PROCEDURE random_seed_parallel
@@ -114 +124 @@
 
    PUBLIC random_number_parallel, random_seed_parallel, random_dummy,          &
-          id_random_array, seq_random_array, init_parallel_random_generator
+          id_random_array, seq_random_array, init_parallel_random_generator,   &
+          random_number_parallel_gauss
 
  CONTAINS
@@ -248 +259 @@
 ! Description:
 ! ------------
+!> Returns in harvest a normally distributed deviate with zero mean and unit
+!> variance, using ran0_s as the source of uniform deviates. Following
+!> Numerical Recipes in Fortran90 (Press et al., 2nd edition, 1996, pp 1152ff).
+!> Note, instead of ran1_s, ran0_s is used.
+!------------------------------------------------------------------------------!
+   SUBROUTINE gasdev_s(harvest)
+
+      REAL(wp), INTENT(OUT) ::  harvest   !<
+
+      REAL(wp) ::  rsq      !<
+      REAL(wp) ::  v1       !<
+      REAL(wp) ::  v2       !<
+      REAL(wp), SAVE ::  g  !<
+
+      LOGICAL, SAVE ::  gaus_stored = .FALSE. !<
+!
+!--   We have an extra deviate handy, so return it, and unset the flag.
+      IF (gaus_stored)  THEN
+         harvest = g
+         gaus_stored = .FALSE.
+!
+!--   We don’t have an extra deviate handy, so pick two uniform numbers in the
+!--   square extending from -1 to +1 in each direction
+      ELSE
+         DO
+            CALL ran0_s(v1)
+            CALL ran0_s(v2)
+            v1 = 2.0_wp * v1 - 1.0_wp
+            v2 = 2.0_wp * v2 - 1.0_wp
+!
+!--         see if they are in the unit circle
+            rsq = v1**2 + v2**2
+!
+!--         otherwise try again.
+            IF (rsq > 0.0  .AND.  rsq < 1.0) EXIT
+         ENDDO
+!
+!--      Now make the Box-Muller transformation to get two normal deviates.
+!--      Return one and save the other for next time. Set flag.
+         rsq = SQRT(-2.0_sp * LOG(rsq)/rsq)
+         harvest = v1 * rsq
+         g = v2 * rsq
+         gaus_stored = .TRUE.
+      ENDIF
+
+   END SUBROUTINE gasdev_s
+
+!------------------------------------------------------------------------------!
+! Description:
+! ------------
 !> Initialize or reinitialize the random generator state space to vectors of size length. 
 !> The saved variable seq is hashed (via calls to the module routine ran_hash)