Initial checkin of gRPC to third_party/

third_party/grpc/src/core/iomgr/time_averaged_stats.c

Index: third_party/grpc/src/core/iomgr/time_averaged_stats.c
diff --git a/third_party/grpc/src/core/iomgr/time_averaged_stats.c b/third_party/grpc/src/core/iomgr/time_averaged_stats.c
new file mode 100644
index 0000000000000000000000000000000000000000..e075db4373515ffbb4f855aafa7672bac461aa55
--- /dev/null
+++ b/third_party/grpc/src/core/iomgr/time_averaged_stats.c
@@ -0,0 +1,77 @@
+/*
+ *
+ * Copyright 2015, Google Inc.
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ *     * Redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer.
+ *     * Redistributions in binary form must reproduce the above
+ * copyright notice, this list of conditions and the following disclaimer
+ * in the documentation and/or other materials provided with the
+ * distribution.
+ *     * Neither the name of Google Inc. nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#include "src/core/iomgr/time_averaged_stats.h"
+
+void grpc_time_averaged_stats_init(grpc_time_averaged_stats* stats,
+                                   double init_avg, double regress_weight,
+                                   double persistence_factor) {
+  stats->init_avg = init_avg;
+  stats->regress_weight = regress_weight;
+  stats->persistence_factor = persistence_factor;
+  stats->batch_total_value = 0;
+  stats->batch_num_samples = 0;
+  stats->aggregate_total_weight = 0;
+  stats->aggregate_weighted_avg = init_avg;
+}
+
+void grpc_time_averaged_stats_add_sample(grpc_time_averaged_stats* stats,
+                                         double value) {
+  stats->batch_total_value += value;
+  ++stats->batch_num_samples;
+}
+
+double grpc_time_averaged_stats_update_average(
+    grpc_time_averaged_stats* stats) {
+  /* Start with the current batch: */
+  double weighted_sum = stats->batch_total_value;
+  double total_weight = stats->batch_num_samples;
+  if (stats->regress_weight > 0) {
+    /* Add in the regression towards init_avg_: */
+    weighted_sum += stats->regress_weight * stats->init_avg;
+    total_weight += stats->regress_weight;
+  }
+  if (stats->persistence_factor > 0) {
+    /* Add in the persistence: */
+    const double prev_sample_weight =
+        stats->persistence_factor * stats->aggregate_total_weight;
+    weighted_sum += prev_sample_weight * stats->aggregate_weighted_avg;
+    total_weight += prev_sample_weight;
+  }
+  stats->aggregate_weighted_avg =
+      (total_weight > 0) ? (weighted_sum / total_weight) : stats->init_avg;
+  stats->aggregate_total_weight = total_weight;
+  stats->batch_num_samples = 0;
+  stats->batch_total_value = 0;
+  return stats->aggregate_weighted_avg;
+}