Warn on lack of CPU cycle counter

SpeedTest.cpp

@@ -265,6 +265,12 @@ double SpeedTest ( pfHash hash, uint32_t seed, const int trials, const int block
   return CalcMean(times);
 }
 
+bool timer_counts_ns ( void )
+{
+  const double ratio = double(timer_start()) / timeofday();
+  return (0.999 < ratio && ratio < 1.001);
+}
+
 //-----------------------------------------------------------------------------
 // 256k blocks seem to give the best results.
 
@@ -273,6 +279,11 @@ void BulkSpeedTest ( pfHash hash, uint32_t seed )
   const int trials = 2999;
   const int blocksize = 256 * 1024;
 
+  if (timer_counts_ns())
+    printf("WARNING: no cycle counter, cycle == 1ns\n");
+  if (timer_start() == timer_end())
+    printf("WARNING: timer resolution is low\n");
+
   printf("Bulk speed test - %d-byte keys\n",blocksize);
   double sumbpc = 0.0;