Cap the max parallelism that user can request (#2681)

src/ngraph/runtime/cpu/cpu_executor.cpp

@@ -20,6 +20,8 @@
 
 #include "ngraph/except.hpp"
 
+#define MAX_PARALLELISM_THRESHOLD 2
+
 static int GetNumCores()
 {
     const auto omp_num_threads = std::getenv("OMP_NUM_THREADS");
@@ -38,6 +40,17 @@ static int GetNumCores()
     {
         count = std::thread::hardware_concurrency() / 2;
     }
+
+    int max_parallelism_allowed = MAX_PARALLELISM_THRESHOLD * std::thread::hardware_concurrency();
+    if (count > max_parallelism_allowed)
+    {
+        throw ngraph::ngraph_error(
+            "OMP_NUM_THREADS and/or NGRAPH_INTRA_OP_PARALLELISM is too high: "
+            "(" +
+            std::to_string(count) + "). Please specify a value in range [1-" +
+            std::to_string(max_parallelism_allowed) + "]");
+    }
+
     return count < 1 ? 1 : count;
 }