BLI: Add utility for tacking average and min runtime

This is useful to save time manually averaging many timing results.
The minimum is included because often it can be more stable than an
average, and it can help to expose calls from other contexts with lower
times that would make the average useless.

Differential Revision: https://developer.blender.org/D14417

source/blender/blenlib/BLI_timeit.hh

@@ -38,6 +38,41 @@ class ScopedTimer {
   }
 };
 
+class ScopedTimerAveraged {
+ private:
+  std::string name_;
+  TimePoint start_;
+
+  int64_t &total_count_;
+  Nanoseconds &total_time_;
+  Nanoseconds &min_time_;
+
+ public:
+  ScopedTimerAveraged(std::string name,
+                      int64_t &total_count,
+                      Nanoseconds &total_time,
+                      Nanoseconds &min_time)
+      : name_(std::move(name)),
+        total_count_(total_count),
+        total_time_(total_time),
+        min_time_(min_time)
+  {
+    start_ = Clock::now();
+  }
+
+  ~ScopedTimerAveraged();
+};
+
 }  // namespace blender::timeit
 
 #define SCOPED_TIMER(name) blender::timeit::ScopedTimer scoped_timer(name)
+
+/**
+ * Print the average and minumum runtime of the timer's scope.
+ * \warning This uses static variables, so it is not thread-safe.
+ */
+#define SCOPED_TIMER_AVERAGED(name) \
+  static int64_t total_count_; \
+  static blender::timeit::Nanoseconds total_time_; \
+  static blender::timeit::Nanoseconds min_time_ = blender::timeit::Nanoseconds::max(); \
+  blender::timeit::ScopedTimerAveraged scoped_timer(name, total_count_, total_time_, min_time_)

source/blender/blenlib/intern/timeit.cc

@@ -2,6 +2,8 @@
 
 #include "BLI_timeit.hh"
 
+#include <algorithm>
+
 namespace blender::timeit {
 
 void print_duration(Nanoseconds duration)
@@ -17,4 +19,20 @@ void print_duration(Nanoseconds duration)
   }
 }
 
+ScopedTimerAveraged::~ScopedTimerAveraged()
+{
+  const TimePoint end = Clock::now();
+  const Nanoseconds duration = end - start_;
+
+  total_count_++;
+  total_time_ += duration;
+  min_time_ = std::min(duration, min_time_);
+
+  std::cout << "Timer '" << name_ << "': (Average: ";
+  print_duration(total_time_ / total_count_);
+  std::cout << ", Min: ";
+  print_duration(min_time_);
+  std::cout << ")\n";
+}
+
 }  // namespace blender::timeit