set gnThreads to 4 in tracker

matdb/matdb/mpiMain.cpp

@@ -238,7 +238,7 @@ int main(int argc, char** argv)
 		fprintf(stderr, "ERROR: could not set busy timeout\n");
 	}
 
-	gnThreads = 2; //  std::thread::hardware_concurrency();
+	gnThreads = 4; //  std::thread::hardware_concurrency();
 	gdbPool = (threadDB*)calloc(gnThreads, sizeof(threadDB));
 
 	startMPI();