First draft of (experimental) benchmarking support

1 files changed, 40 insertions, 14 deletions

diff --git a/include/internal/catch_timer.cpp b/include/internal/catch_timer.cpp
index ca09d7bc..9635ccea 100644
--- a/include/internal/catch_timer.cpp
+++ b/include/internal/catch_timer.cpp
@@ -16,21 +16,47 @@ namespace Catch {
         return std::chrono::duration_cast<std::chrono::nanoseconds>( std::chrono::high_resolution_clock::now().time_since_epoch() ).count();
     }
 
-        void Timer::start() {
-           m_nanoseconds = getCurrentNanosecondsSinceEpoch();
-        }
-        auto Timer::getElapsedNanoseconds() const -> unsigned int {
-            return static_cast<unsigned int>(getCurrentNanosecondsSinceEpoch() - m_nanoseconds);
-        }
-        auto Timer::getElapsedMicroseconds() const -> unsigned int {
-            return static_cast<unsigned int>(getElapsedNanoseconds()/1000);
-        }
-        auto Timer::getElapsedMilliseconds() const -> unsigned int {
-            return static_cast<unsigned int>(getElapsedMicroseconds()/1000);
-        }
-        auto Timer::getElapsedSeconds() const -> double {
-            return getElapsedMicroseconds()/1000000.0;
+    auto estimateClockResolution() -> double {
+        uint64_t sum = 0;
+        static const uint64_t iterations = 1000000;
+
+        for( size_t i = 0; i < iterations; ++i ) {
+
+            uint64_t ticks;
+            uint64_t baseTicks = getCurrentNanosecondsSinceEpoch();
+            do {
+                ticks = getCurrentNanosecondsSinceEpoch();
+            }
+            while( ticks == baseTicks );
+
+            auto delta = ticks - baseTicks;
+            sum += delta;
         }
 
+        // We're just taking the mean, here. To do better we could take the std. dev and exclude outliers
+        // - and potentially do more iterations if there's a high variance.
+        return sum/(double)iterations;
+    }
+    auto getEstimatedClockResolution() -> double {
+        static auto s_resolution = estimateClockResolution();
+        return s_resolution;
+    }
+
+    void Timer::start() {
+       m_nanoseconds = getCurrentNanosecondsSinceEpoch();
+    }
+    auto Timer::getElapsedNanoseconds() const -> unsigned int {
+        return static_cast<unsigned int>(getCurrentNanosecondsSinceEpoch() - m_nanoseconds);
+    }
+    auto Timer::getElapsedMicroseconds() const -> unsigned int {
+        return static_cast<unsigned int>(getElapsedNanoseconds()/1000);
+    }
+    auto Timer::getElapsedMilliseconds() const -> unsigned int {
+        return static_cast<unsigned int>(getElapsedMicroseconds()/1000);
+    }
+    auto Timer::getElapsedSeconds() const -> double {
+        return getElapsedMicroseconds()/1000000.0;
+    }
+
 
 } // namespace Catch