1 /* 2 * Copyright (C) 2013 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef ART_RUNTIME_BASE_HISTOGRAM_INL_H_ 18 #define ART_RUNTIME_BASE_HISTOGRAM_INL_H_ 19 20 #include "histogram.h" 21 22 #include "utils.h" 23 24 #include <algorithm> 25 #include <cmath> 26 #include <limits> 27 #include <ostream> 28 29 namespace art { 30 31 template <class Value> inline void Histogram<Value>::AddValue(Value value) { 32 CHECK_GE(value, static_cast<Value>(0)); 33 if (value >= max_) { 34 Value new_max = ((value + 1) / bucket_width_ + 1) * bucket_width_; 35 DCHECK_GT(new_max, max_); 36 GrowBuckets(new_max); 37 } 38 39 BucketiseValue(value); 40 } 41 42 template <class Value> inline Histogram<Value>::Histogram(const char* name) 43 : kAdjust(0), 44 kInitialBucketCount(0), 45 name_(name), 46 max_buckets_(0) { 47 } 48 49 template <class Value> 50 inline Histogram<Value>::Histogram(const char* name, Value initial_bucket_width, 51 size_t max_buckets) 52 : kAdjust(1000), 53 kInitialBucketCount(8), 54 name_(name), 55 max_buckets_(max_buckets), 56 bucket_width_(initial_bucket_width) { 57 Reset(); 58 } 59 60 template <class Value> 61 inline void Histogram<Value>::GrowBuckets(Value new_max) { 62 while (max_ < new_max) { 63 // If we have reached the maximum number of buckets, merge buckets together. 64 if (frequency_.size() >= max_buckets_) { 65 CHECK(IsAligned<2>(frequency_.size())); 66 // We double the width of each bucket to reduce the number of buckets by a factor of 2. 67 bucket_width_ *= 2; 68 const size_t limit = frequency_.size() / 2; 69 // Merge the frequencies by adding each adjacent two together. 70 for (size_t i = 0; i < limit; ++i) { 71 frequency_[i] = frequency_[i * 2] + frequency_[i * 2 + 1]; 72 } 73 // Remove frequencies in the second half of the array which were added to the first half. 74 while (frequency_.size() > limit) { 75 frequency_.pop_back(); 76 } 77 } 78 max_ += bucket_width_; 79 frequency_.push_back(0); 80 } 81 } 82 83 template <class Value> inline size_t Histogram<Value>::FindBucket(Value val) const { 84 // Since this is only a linear histogram, bucket index can be found simply with 85 // dividing the value by the bucket width. 86 DCHECK_GE(val, min_); 87 DCHECK_LE(val, max_); 88 const size_t bucket_idx = static_cast<size_t>((val - min_) / bucket_width_); 89 DCHECK_GE(bucket_idx, 0ul); 90 DCHECK_LE(bucket_idx, GetBucketCount()); 91 return bucket_idx; 92 } 93 94 template <class Value> 95 inline void Histogram<Value>::BucketiseValue(Value val) { 96 CHECK_LT(val, max_); 97 sum_ += val; 98 sum_of_squares_ += val * val; 99 ++sample_size_; 100 ++frequency_[FindBucket(val)]; 101 max_value_added_ = std::max(val, max_value_added_); 102 min_value_added_ = std::min(val, min_value_added_); 103 } 104 105 template <class Value> inline void Histogram<Value>::Initialize() { 106 for (size_t idx = 0; idx < kInitialBucketCount; idx++) { 107 frequency_.push_back(0); 108 } 109 // Cumulative frequency and ranges has a length of 1 over frequency. 110 max_ = bucket_width_ * GetBucketCount(); 111 } 112 113 template <class Value> inline size_t Histogram<Value>::GetBucketCount() const { 114 return frequency_.size(); 115 } 116 117 template <class Value> inline void Histogram<Value>::Reset() { 118 sum_of_squares_ = 0; 119 sample_size_ = 0; 120 min_ = 0; 121 sum_ = 0; 122 min_value_added_ = std::numeric_limits<Value>::max(); 123 max_value_added_ = std::numeric_limits<Value>::min(); 124 frequency_.clear(); 125 Initialize(); 126 } 127 128 template <class Value> inline Value Histogram<Value>::GetRange(size_t bucket_idx) const { 129 DCHECK_LE(bucket_idx, GetBucketCount()); 130 return min_ + bucket_idx * bucket_width_; 131 } 132 133 template <class Value> inline double Histogram<Value>::Mean() const { 134 DCHECK_GT(sample_size_, 0ull); 135 return static_cast<double>(sum_) / static_cast<double>(sample_size_); 136 } 137 138 template <class Value> inline double Histogram<Value>::Variance() const { 139 DCHECK_GT(sample_size_, 0ull); 140 // Using algorithms for calculating variance over a population: 141 // http://en.wikipedia.org/wiki/Algorithms_for_calculating_variance 142 Value sum_squared = sum_ * sum_; 143 double sum_squared_by_n_squared = 144 static_cast<double>(sum_squared) / 145 static_cast<double>(sample_size_ * sample_size_); 146 double sum_of_squares_by_n = 147 static_cast<double>(sum_of_squares_) / static_cast<double>(sample_size_); 148 return sum_of_squares_by_n - sum_squared_by_n_squared; 149 } 150 151 template <class Value> 152 inline void Histogram<Value>::PrintBins(std::ostream& os, const CumulativeData& data) const { 153 DCHECK_GT(sample_size_, 0ull); 154 for (size_t bin_idx = 0; bin_idx < data.freq_.size(); ++bin_idx) { 155 if (bin_idx > 0 && data.perc_[bin_idx] == data.perc_[bin_idx - 1]) { 156 bin_idx++; 157 continue; 158 } 159 os << GetRange(bin_idx) << ": " << data.freq_[bin_idx] << "\t" 160 << data.perc_[bin_idx] * 100.0 << "%\n"; 161 } 162 } 163 164 template <class Value> 165 inline void Histogram<Value>::PrintConfidenceIntervals(std::ostream &os, double interval, 166 const CumulativeData& data) const { 167 static constexpr size_t kFractionalDigits = 3; 168 DCHECK_GT(interval, 0); 169 DCHECK_LT(interval, 1.0); 170 const double per_0 = (1.0 - interval) / 2.0; 171 const double per_1 = per_0 + interval; 172 const TimeUnit unit = GetAppropriateTimeUnit(Mean() * kAdjust); 173 os << Name() << ":\tSum: " << PrettyDuration(Sum() * kAdjust) << " " 174 << (interval * 100) << "% C.I. " << FormatDuration(Percentile(per_0, data) * kAdjust, unit, 175 kFractionalDigits) 176 << "-" << FormatDuration(Percentile(per_1, data) * kAdjust, unit, kFractionalDigits) << " " 177 << "Avg: " << FormatDuration(Mean() * kAdjust, unit, kFractionalDigits) << " Max: " 178 << FormatDuration(Max() * kAdjust, unit, kFractionalDigits) << "\n"; 179 } 180 181 template <class Value> 182 inline void Histogram<Value>::CreateHistogram(CumulativeData* out_data) const { 183 DCHECK_GT(sample_size_, 0ull); 184 out_data->freq_.clear(); 185 out_data->perc_.clear(); 186 uint64_t accumulated = 0; 187 out_data->freq_.push_back(accumulated); 188 out_data->perc_.push_back(0.0); 189 for (size_t idx = 0; idx < frequency_.size(); idx++) { 190 accumulated += frequency_[idx]; 191 out_data->freq_.push_back(accumulated); 192 out_data->perc_.push_back(static_cast<double>(accumulated) / static_cast<double>(sample_size_)); 193 } 194 DCHECK_EQ(out_data->freq_.back(), sample_size_); 195 DCHECK_LE(std::abs(out_data->perc_.back() - 1.0), 0.001); 196 } 197 198 template <class Value> 199 inline double Histogram<Value>::Percentile(double per, const CumulativeData& data) const { 200 DCHECK_GT(data.perc_.size(), 0ull); 201 size_t upper_idx = 0, lower_idx = 0; 202 for (size_t idx = 0; idx < data.perc_.size(); idx++) { 203 if (per <= data.perc_[idx]) { 204 upper_idx = idx; 205 break; 206 } 207 208 if (per >= data.perc_[idx] && idx != 0 && data.perc_[idx] != data.perc_[idx - 1]) { 209 lower_idx = idx; 210 } 211 } 212 213 const double lower_perc = data.perc_[lower_idx]; 214 const double lower_value = static_cast<double>(GetRange(lower_idx)); 215 if (per == lower_perc) { 216 return lower_value; 217 } 218 219 const double upper_perc = data.perc_[upper_idx]; 220 const double upper_value = static_cast<double>(GetRange(upper_idx)); 221 if (per == upper_perc) { 222 return upper_value; 223 } 224 DCHECK_GT(upper_perc, lower_perc); 225 226 double value = lower_value + (upper_value - lower_value) * 227 (per - lower_perc) / (upper_perc - lower_perc); 228 229 if (value < min_value_added_) { 230 value = min_value_added_; 231 } else if (value > max_value_added_) { 232 value = max_value_added_; 233 } 234 235 return value; 236 } 237 238 } // namespace art 239 #endif // ART_RUNTIME_BASE_HISTOGRAM_INL_H_ 240 241
