adding new faabric mpi main macro

examples/mpi_helloworld.cpp

@@ -3,11 +3,60 @@
 
 #include <unistd.h>
 
-int main()
+#define FAABRIC_MPI_MAIN()
+class _Executor final : public FaabricExecutor
 {
-    faabric::util::initLogging();
+    public:
+        explicit _Executor() : FaabricExecutor(0) {}
+
+        bool doExecute(faabric::Message& msg) override
+        {
+            return _execMpiFunc();
+        }
+};
+class _SingletonPool : public FaabricPool
+{
+    public:
+        explicit _SingletonPool() : FaabricPool(1) {}
+
+        std::unique_ptr<FaabricExecutor> createExecutor(int threadIdx) override
+        {
+            return std::make_unique<_Executor>(threadIdx);
+        }
+};
+int main(int argc, char** argv)
+{
+    faabric::util::initLogging()
     auto logger = faabric::util::getLogger();
+    auto scheduler = faabric::scheduler::getScheduler();
+    auto conf = faabric::util::getSystemConfig();
+
+    // Add host to the global set
+    scheduler.addHostToGlobalSet();
+
+    // Print current configuration
+    conf.print();
+
+    // Start the thread pool (nThreads == 1) and the state and function
+    // call servers.
+    _SingletonPool p();
+    p.startThreadPool();
+    p.startStateServer();
+    p.startFunctionCallServer();
 
+    const char* funcName = "hellompi";
+    auto msg = faabric::util::messageFactory("mpi", funcName);
+    msg.set_mpiworldsize(1);
+
+    // Shutdown
+    scheduler.clear();
+    p.shutdown();
+}
+
+bool _execMpiFunc(int argc, char** argv)
+
+FAABRIC_MPI_MAIN
+{
     MPI_Init(NULL, NULL);
 
     int rank, worldSize;

examples/mpi_runner.cpp

@@ -5,6 +5,7 @@
 
 #define EXAMPLE_BUILD_PATH "/code/faabric/examples/build"
 
+
 // Macro defined in include/faabric/executor/FaabricPool.h
 // bool _execFunc(faabric::Message& msg)
 FAABRIC_EXECUTOR