Use reliable PRNG instead of plain random.

* random is subject to arbitrary disturbances because libraries like to
  assume it can be used indiscriminately.

tests/deco2d_model.c

@@ -158,7 +158,7 @@ modelRun(struct model_config setup, MPI_Comm comm)
   varDesc = (struct varDesc_t *)Malloc(nVars * sizeof (varDesc[0]));
   for (size_t varIdx = 0; varIdx < nVars; varIdx++ )
     {
-      int varLevs = (int)random()%4;
+      int varLevs = (int)cdi_repeatable_random()%4;
       switch (varLevs)
         {
         case 1:
@@ -276,7 +276,7 @@ modelRun(struct model_config setup, MPI_Comm comm)
       varDesc[varIdx].code = GRIB_USERDEF + (int)varIdx;
       vlistDefVarCode(vlistID, varDesc[varIdx].id, varDesc[varIdx].code);
       vlistDefVarDatatype(vlistID, varDesc[varIdx].id, setup.datatype);
-      varDesc[varIdx].useFloat = (bool)(random()&1);
+      varDesc[varIdx].useFloat = (bool)(cdi_repeatable_random()&1);
     }
 
   taxisID = taxisCreate ( setup.taxistype );

tests/pio_write.c

@@ -25,6 +25,7 @@
 #include "error.h"
 #include "dmemory.h"
 #include "pio_write.h"
+#include "simple_model_helper.h"
 #ifdef USE_MPI
 #include "cdipio.h"
 #include "pio_util.h"
@@ -495,7 +496,7 @@ int main(int argc, char *argv[])
 #ifdef USE_MPI
   MPI_Bcast(&randSeed, 1, MPI_UNSIGNED, 0, MPI_COMM_WORLD);
 #endif
-  srandom(randSeed);
+  cdi_seed_repeatable_random(randSeed);
 #ifdef USE_MPI
   if (rankGlob == 0)
 #endif
@@ -520,6 +521,7 @@ int main(int argc, char *argv[])
 
 #ifdef USE_MPI
     }
+  cdi_repeatable_finalize();
   pioFinalize ();
   namespaceSetActive(initNamespace);
   cdiPioConfDestroy(pioConfHandle);

tests/simple_model.c

@@ -116,7 +116,7 @@ modelRun(struct model_config setup, MPI_Comm comm)
   varDesc = (struct varDesc_t *)Malloc(nVars * sizeof (varDesc[0]));
   for (size_t varIdx = 0; varIdx < nVars; varIdx++ )
     {
-      int varLevs = (int)random()%4;
+      int varLevs = (int)cdi_repeatable_random()%4;
       switch (varLevs)
         {
         case 1:
@@ -186,7 +186,7 @@ modelRun(struct model_config setup, MPI_Comm comm)
       varDesc[varIdx].code = GRIB_USERDEF + (int)varIdx;
       vlistDefVarCode(vlistID, varDesc[varIdx].id, varDesc[varIdx].code);
       vlistDefVarDatatype(vlistID, varDesc[varIdx].id, setup.datatype);
-      varDesc[varIdx].useFloat = (bool)(random()&1);
+      varDesc[varIdx].useFloat = (bool)(cdi_repeatable_random()&1);
     }
 
   taxisID = taxisCreate ( setup.taxistype );

tests/simple_model_helper.c

@@ -296,6 +296,26 @@ PPM_prime_factorization_32(uint32_t n, uint32_t **factors)
   *factors = pfactors;
   return numFactors;
 }
+
+#endif
+
+#ifndef HAVE_PPM_CORE
+static char repeatable_rand_state[31 * sizeof (long)];
+
+long cdi_repeatable_random(void)
+{
+  char *caller_rand_state = setstate(repeatable_rand_state);
+  long retval = random();
+  setstate(caller_rand_state);
+  return retval;
+}
+
+void cdi_seed_repeatable_random(unsigned seed)
+{
+  char *caller_rand_state = initstate(seed, repeatable_rand_state,
+                                      sizeof (repeatable_rand_state));
+  setstate(caller_rand_state);
+}
 #endif
 
 /*

tests/simple_model_helper.h

@@ -93,4 +93,33 @@ PPM_prime_factorization_32(uint32_t n, uint32_t **factors);
 
 #endif
 
+#ifdef HAVE_PPM_CORE
+#  include <ppm/ppm.h>
+#  include <core/ppm_random.h>
+#  ifdef _OPENMP
+#    define cdi_omp_pragma(prg) _Pragma(prg)
+#  else
+#    define cdi_omp_pragma(prg)
+#  endif
+#  define cdi_seed_repeatable_random(seed) do {          \
+    int seed_ = (int)seed;                               \
+    MPI_Comm comm_ = MPI_COMM_WORLD;                     \
+    cdi_omp_pragma("omp parallel")                       \
+      if ((!PPM_initialized() || PPM_finalized()))       \
+        PPM_initialize(&comm_, &seed_, NULL);            \
+      else                                               \
+        PPM_ya_rand_init(MPI_COMM_WORLD, seed_);         \
+  } while (0)
+#  define cdi_repeatable_random() ((long)(PPM_irandp()))
+#  define cdi_repeatable_finalize() PPM_finalize()
+
+#else
+/* add random-wrapper to make call results repeatable, if PPM_random
+ * can't be used */
+void cdi_seed_repeatable_random(unsigned seed);
+long cdi_repeatable_random(void);
+#  define cdi_repeatable_finalize() do {        \
+  } while (0)
+#endif
+
 #endif