croposp [MERGE]: merge improved random number generator from master

src/libs/libtf/tf_gsl_rnd.c

@@ -31,11 +31,15 @@
  * REVISIONS and CHANGES 
  *  - 07/05/2007   V1.0   Thomas Forbriger
  *  - 13/11/2010   V1.1   changed name of file
+ *  - 14/02/2019   V1.2   change seeding mechanism
+ *                        accept default seed value provided through
+ *                        environment variable; if no default is set, use
+ *                        nanoseconds to seed
  * 
  * ============================================================================
  */
 #define TF_TF_GSL_RND_C_CC_VERSION \
-  "TF_TF_GSL_RND_C_CC   V1.1"
+  "TF_TF_GSL_RND_C_CC   V1.2"
 #define TF_TF_GSL_RND_C_CC_CVSID \
   "$Id$"
 
@@ -55,13 +59,19 @@ int tf_gsl_rng_ugaussian__(doublereal* a, integer* n)
     int i;
     /* set the default type of random number generator 
      * controlled by the environment variable GSL_RNG_TYPE
-     * and allocate a random number generator
+     * seed value can be controlled by GSL_RNG_SEED
      */
     gsl_rng_env_setup();
+    /* seed the generator with the current time if seed is 
+     * not set on command line */
+    if (gsl_rng_default_seed == 0) {
+      struct timespec tp;
+      clock_gettime(CLOCK_REALTIME, &tp);
+      gsl_rng_default_seed = tp.tv_nsec + time(0) ;
+    }
     const gsl_rng_type* T=gsl_rng_default;
+    /* and allocate a random number generator */
     gsl_rng* R=gsl_rng_alloc(T);
-    /* seed the generator with the current time */
-    gsl_rng_set(R, time(0));
     /* read values from the generator, using the desired distribution */
     for (i=0; i<=*n; ++i)
     { a[i]=(doublereal)gsl_ran_ugaussian(R); }
@@ -81,13 +91,19 @@ int tf_gsl_rng_uniform__(doublereal* a, integer* n)
     int i;
     /* set the default type of random number generator 
      * controlled by the environment variable GSL_RNG_TYPE
-     * and allocate a random number generator
+     * seed value can be controlled by GSL_RNG_SEED
      */
     gsl_rng_env_setup();
+    /* seed the generator with the current time if seed is 
+     * not set on command line */
+    if (gsl_rng_default_seed == 0) {
+      struct timespec tp;
+      clock_gettime(CLOCK_REALTIME, &tp);
+      gsl_rng_default_seed = tp.tv_nsec + time(0) ;
+    }
     const gsl_rng_type* T=gsl_rng_default;
+    /* and allocate a random number generator */
     gsl_rng* R=gsl_rng_alloc(T);
-    /* seed the generator with the current time */
-    gsl_rng_set(R, time(0));
     /* read values from the generator, using the desired distribution */
     for (i=0; i<=*n; ++i)
     { a[i]=(doublereal)gsl_rng_uniform(R); }