3 files changed, 53 insertions, 38 deletions

diff --git a/src/build.cc b/src/build.cc
index e1aaad1..5a0c3b3 100644
--- a/src/build.cc
+++ b/src/build.cc
@@ -42,8 +42,7 @@ BuildStatus::BuildStatus(const BuildConfig& config)
       start_time_millis_(GetTimeMillis()),
       started_edges_(0), finished_edges_(0), total_edges_(0),
       have_blank_line_(true), progress_status_format_(NULL),
-      overall_rate_(), current_rate_(),
-      current_rate_average_count_(config.parallelism) {
+      overall_rate_(), current_rate_(config.parallelism) {
 #ifndef _WIN32
   const char* term = getenv("TERM");
   smart_terminal_ = isatty(1) && term && string(term) != "dumb";
@@ -136,7 +135,8 @@ void BuildStatus::BuildFinished() {
     printf("\n");
 }
 
-string BuildStatus::FormatProgressStatus(const char* progress_status_format) const {
+string BuildStatus::FormatProgressStatus(
+    const char* progress_status_format) const {
   string out;
   char buf[32];
   for (const char* s = progress_status_format; *s != '\0'; ++s) {
@@ -177,30 +177,24 @@ string BuildStatus::FormatProgressStatus(const char* progress_status_format) con
         out += buf;
         break;
 
-      // Overall finished edges per second.
+        // Overall finished edges per second.
       case 'o':
-        overall_rate_.UpdateRate(finished_edges_, finished_edges_);
+        overall_rate_.UpdateRate(finished_edges_);
         overall_rate_.snprinfRate(buf, "%.1f");
         out += buf;
         break;
 
-      // Current rate, average over the last '-j' jobs.
+        // Current rate, average over the last '-j' jobs.
       case 'c':
-        // TODO use sliding window?
-        if (finished_edges_ > current_rate_.last_update() &&
-            finished_edges_ - current_rate_.last_update() == current_rate_average_count_) {
-          current_rate_.UpdateRate(current_rate_average_count_, finished_edges_);
-          current_rate_.Restart();
-        }
-        current_rate_.snprinfRate(buf, "%.0f");
+        current_rate_.UpdateRate(finished_edges_);
+        current_rate_.snprinfRate(buf, "%.1f");
         out += buf;
         break;
 
-      default: {
+      default:
         Fatal("unknown placeholder '%%%c' in $NINJA_STATUS", *s);
         return "";
       }
-      }
     } else {
       out.push_back(*s);
     }
diff --git a/src/build.h b/src/build.h
index 3e7a144..0902a4c 100644
--- a/src/build.h
+++ b/src/build.h
@@ -201,37 +201,59 @@ struct BuildStatus {
   const char* progress_status_format_;
 
   struct RateInfo {
-    RateInfo() : last_update_(0), rate_(-1) {}
-
-    double rate() const { return rate_; }
-    int last_update() const { return last_update_; }
-    void Restart() { return stopwatch_.Restart(); }
-
-    double UpdateRate(int edges, int update_hint) {
-      if (update_hint != last_update_) {
-        rate_ = edges / stopwatch_.Elapsed() + 0.5;
-        last_update_ = update_hint;
-      }
-      return rate_;
+    RateInfo() : rate_(-1) {}
+
+    void Restart() { stopwatch_.Restart(); }
+
+    void UpdateRate(int edges) {
+      if (edges && stopwatch_.Elapsed())
+        rate_ = edges / stopwatch_.Elapsed();
+    }
+
+    template<class T>
+    void snprinfRate(T buf, const char* format) {
+      if (rate_ == -1) snprintf(buf, sizeof(buf), "?");
+      else             snprintf(buf, sizeof(buf), format, rate_);
+    }
+
+  private:
+    Stopwatch stopwatch_;
+    double rate_;
+  };
+
+  struct SlidingRateInfo {
+    SlidingRateInfo(int n) : N(n), last_update_(-1), rate_(-1) {}
+
+    void Restart() { stopwatch_.Restart(); }
+
+    void UpdateRate(int update_hint) {
+      if (update_hint == last_update_)
+        return;
+      last_update_ = update_hint;
+
+      if (times_.size() == N)
+        times_.pop();
+      times_.push(stopwatch_.Elapsed());
+      if (times_.back() != times_.front())
+        rate_ = times_.size() / (times_.back() - times_.front());
     }
 
     template<class T>
     void snprinfRate(T buf, const char* format) {
-      if (rate_ == -1)
-        snprintf(buf, sizeof(buf), "?");
-      else
-        snprintf(buf, sizeof(buf), format, rate_);
+      if (rate_ == -1) snprintf(buf, sizeof(buf), "?");
+      else             snprintf(buf, sizeof(buf), format, rate_);
     }
 
   private:
+    const size_t N;
+    std::queue<double> times_;
     Stopwatch stopwatch_;
     int last_update_;
     double rate_;
   };
 
   mutable RateInfo overall_rate_;
-  mutable RateInfo current_rate_;
-  const int current_rate_average_count_;
+  mutable SlidingRateInfo current_rate_;
 
 #ifdef _WIN32
   void* console_;
diff --git a/src/metrics.h b/src/metrics.h
index f5ac0de..a4ef9f7 100644
--- a/src/metrics.h
+++ b/src/metrics.h
@@ -59,19 +59,18 @@ private:
 };
 
 /// Get the current time as relative to some epoch.
-/// Epoch varies between platforms; only useful for measuring elapsed
-/// time.
+/// Epoch varies between platforms; only useful for measuring elapsed time.
 int64_t GetTimeMillis();
 
 
-/// A simple stopwatch which retruns the time
-// in seconds since Restart() was called
+/// A simple stopwatch which returns the time
+/// in seconds since Restart() was called.
 class Stopwatch
 {
 public:
   Stopwatch() : started_(0) {}
 
-  /// Seconds since Restart() call
+  /// Seconds since Restart() call.
   double Elapsed() const { return 1e-6 * static_cast<double>(Now() - started_); }
 
   void Restart() { started_ = Now(); }