Update NCCL tests

src/timer.h

@@ -0,0 +1,15 @@
+#ifndef _408319ecdd5b47b28bf8f511c4fdf816
+#define _408319ecdd5b47b28bf8f511c4fdf816
+
+#include <cstdint>
+
+// Can't include <chrono> because of bug with gcc 10.3.0
+class timer {
+  std::uint64_t t0;
+public:
+  timer();
+  double elapsed() const;
+  double reset();
+};
+
+#endif