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

@@ -150,7 +150,7 @@ 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: varLevs = setup.max_nlev / 3; break;
@@ -240,7 +240,7 @@ 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"
@@ -422,7 +423,7 @@ 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
@@ -446,6 +447,7 @@ main(int argc, char *argv[])
 
 #ifdef USE_MPI
     }
+  cdi_repeatable_finalize();
   pioFinalize();
   namespaceSetActive(initNamespace);
   cdiPioConfDestroy(pioConfHandle);

tests/simple_model.c

@@ -115,7 +115,7 @@ 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: varLevs = setup.max_nlev / 3; break;
@@ -171,7 +171,7 @@ 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

@@ -253,6 +253,27 @@ 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

@@ -77,4 +77,36 @@ int 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