add main function to invoke GPU memory check

main.cu

@@ -10,4 +10,9 @@ void checkGpuMem() {
     total_m=(uint)total_t/1048576.0;
     used_m=total_m-free_m;
     printf("GPU memory usage: used = %f, free = %f MB, total = %f MB\n",used_m,free_m,total_m);
+}
+
+int main() {
+    checkGpuMem();
+    return 0;
 }