Add assert that we are not inside threaded region when InitRandom is called. (AMReX-Codes#3204)

Author: atmyers

Src/Base/AMReX_Random.cpp

@@ -67,6 +67,12 @@ InitRandom (ULong cpu_seed, int nprocs, ULong gpu_seed)
     nthreads = OpenMP::get_max_threads();
     generators.resize(nthreads);
 
+#ifdef AMREX_USE_OMP
+    if (omp_in_parallel()) {
+        amrex::Abort("It is not safe to call amrex::InitRandom inside a threaded region.");
+    }
+#endif
+
 #ifdef AMREX_USE_OMP
 #pragma omp parallel
 #endif