| /* |
| * |
| * Copyright 2015 gRPC authors. |
| * |
| * Licensed under the Apache License, Version 2.0 (the "License"); |
| * you may not use this file except in compliance with the License. |
| * You may obtain a copy of the License at |
| * |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * |
| * Unless required by applicable law or agreed to in writing, software |
| * distributed under the License is distributed on an "AS IS" BASIS, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| * |
| */ |
| |
| #ifndef GRPC_CORE_LIB_IOMGR_TIME_AVERAGED_STATS_H |
| #define GRPC_CORE_LIB_IOMGR_TIME_AVERAGED_STATS_H |
| |
| /* This tracks a time-decaying weighted average. It works by collecting |
| batches of samples and then mixing their average into a time-decaying |
| weighted mean. It is designed for batch operations where we do many adds |
| before updating the average. */ |
| |
| typedef struct { |
| /* The initial average value. This is the reported average until the first |
| grpc_time_averaged_stats_update_average call. If a positive regress_weight |
| is used, we also regress towards this value on each update. */ |
| double init_avg; |
| /* The sample weight of "init_avg" that is mixed in with each call to |
| grpc_time_averaged_stats_update_average. If the calls to |
| grpc_time_averaged_stats_add_sample stop, this will cause the average to |
| regress back to the mean. This should be non-negative. Set it to 0 to |
| disable the bias. A value of 1 has the effect of adding in 1 bonus sample |
| with value init_avg to each sample period. */ |
| double regress_weight; |
| /* This determines the rate of decay of the time-averaging from one period |
| to the next by scaling the aggregate_total_weight of samples from prior |
| periods when combining with the latest period. It should be in the range |
| [0,1]. A higher value adapts more slowly. With a value of 0.5, if the |
| batches each have k samples, the samples_in_avg_ will grow to 2 k, so the |
| weighting of the time average will eventually be 1/3 new batch and 2/3 |
| old average. */ |
| double persistence_factor; |
| |
| /* The total value of samples since the last UpdateAverage(). */ |
| double batch_total_value; |
| /* The number of samples since the last UpdateAverage(). */ |
| double batch_num_samples; |
| /* The time-decayed sum of batch_num_samples_ over previous batches. This is |
| the "weight" of the old aggregate_weighted_avg_ when updating the |
| average. */ |
| double aggregate_total_weight; |
| /* A time-decayed average of the (batch_total_value_ / batch_num_samples_), |
| computed by decaying the samples_in_avg_ weight in the weighted average. */ |
| double aggregate_weighted_avg; |
| } grpc_time_averaged_stats; |
| |
| /* See the comments on the members above for an explanation of init_avg, |
| regress_weight, and persistence_factor. */ |
| void grpc_time_averaged_stats_init(grpc_time_averaged_stats* stats, |
| double init_avg, double regress_weight, |
| double persistence_factor); |
| /* Add a sample to the current batch. */ |
| void grpc_time_averaged_stats_add_sample(grpc_time_averaged_stats* stats, |
| double value); |
| /* Complete a batch and compute the new estimate of the average sample |
| value. */ |
| double grpc_time_averaged_stats_update_average(grpc_time_averaged_stats* stats); |
| |
| #endif /* GRPC_CORE_LIB_IOMGR_TIME_AVERAGED_STATS_H */ |