Warn on lack of CPU cycle counter

rurban · Jul 11, 2024 · 6bd4345 · 6bd4345
1 parent 67fc076
commit 6bd4345
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Showing 2 changed files with 11 additions and 0 deletions.
diff --git a/Platform.h b/Platform.h
@@ -57,6 +57,7 @@ void SetAffinity ( int cpu );
 
 #pragma intrinsic(__rdtsc)
 // Read Time Stamp Counter
+#define timer_counts_ns() (false)
 #define rdtsc()       __rdtsc()
 #define timer_start() __rdtsc()
 #define timer_end()   __rdtsc()
@@ -251,6 +252,11 @@ __inline__ uint64_t timer_end()
 #endif
 }
 
+__inline__ bool timer_counts_ns ( void )
+{
+  const double ratio = double(timer_start()) / timeofday();
+  return (0.999 < ratio && ratio < 1.001);
+}
 
 #include <strings.h>
 #define _stricmp strcasecmp

diff --git a/SpeedTest.cpp b/SpeedTest.cpp
@@ -273,6 +273,11 @@ 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;