diff options
Diffstat (limited to 'util/histogram.cc')
| -rw-r--r-- | util/histogram.cc | 272 |
1 files changed, 272 insertions, 0 deletions
diff --git a/util/histogram.cc b/util/histogram.cc new file mode 100644 index 0000000..7af4030 --- /dev/null +++ b/util/histogram.cc @@ -0,0 +1,272 @@ +// Copyright (c) 2011 The LevelDB Authors. All rights reserved. +// Use of this source code is governed by a BSD-style license that can be +// found in the LICENSE file. See the AUTHORS file for names of contributors. + +#include "util/histogram.h" + +#include <cmath> +#include <cstdio> + +#include "port/port.h" + +namespace leveldb { + +const double Histogram::kBucketLimit[kNumBuckets] = { + 1, + 2, + 3, + 4, + 5, + 6, + 7, + 8, + 9, + 10, + 12, + 14, + 16, + 18, + 20, + 25, + 30, + 35, + 40, + 45, + 50, + 60, + 70, + 80, + 90, + 100, + 120, + 140, + 160, + 180, + 200, + 250, + 300, + 350, + 400, + 450, + 500, + 600, + 700, + 800, + 900, + 1000, + 1200, + 1400, + 1600, + 1800, + 2000, + 2500, + 3000, + 3500, + 4000, + 4500, + 5000, + 6000, + 7000, + 8000, + 9000, + 10000, + 12000, + 14000, + 16000, + 18000, + 20000, + 25000, + 30000, + 35000, + 40000, + 45000, + 50000, + 60000, + 70000, + 80000, + 90000, + 100000, + 120000, + 140000, + 160000, + 180000, + 200000, + 250000, + 300000, + 350000, + 400000, + 450000, + 500000, + 600000, + 700000, + 800000, + 900000, + 1000000, + 1200000, + 1400000, + 1600000, + 1800000, + 2000000, + 2500000, + 3000000, + 3500000, + 4000000, + 4500000, + 5000000, + 6000000, + 7000000, + 8000000, + 9000000, + 10000000, + 12000000, + 14000000, + 16000000, + 18000000, + 20000000, + 25000000, + 30000000, + 35000000, + 40000000, + 45000000, + 50000000, + 60000000, + 70000000, + 80000000, + 90000000, + 100000000, + 120000000, + 140000000, + 160000000, + 180000000, + 200000000, + 250000000, + 300000000, + 350000000, + 400000000, + 450000000, + 500000000, + 600000000, + 700000000, + 800000000, + 900000000, + 1000000000, + 1200000000, + 1400000000, + 1600000000, + 1800000000, + 2000000000, + 2500000000.0, + 3000000000.0, + 3500000000.0, + 4000000000.0, + 4500000000.0, + 5000000000.0, + 6000000000.0, + 7000000000.0, + 8000000000.0, + 9000000000.0, + 1e200, +}; + +void Histogram::Clear() { + min_ = kBucketLimit[kNumBuckets - 1]; + max_ = 0; + num_ = 0; + sum_ = 0; + sum_squares_ = 0; + for (int i = 0; i < kNumBuckets; i++) { + buckets_[i] = 0; + } +} + +void Histogram::Add(double value) { + // Linear search is fast enough for our usage in db_bench + int b = 0; + while (b < kNumBuckets - 1 && kBucketLimit[b] <= value) { + b++; + } + buckets_[b] += 1.0; + if (min_ > value) min_ = value; + if (max_ < value) max_ = value; + num_++; + sum_ += value; + sum_squares_ += (value * value); +} + +void Histogram::Merge(const Histogram& other) { + if (other.min_ < min_) min_ = other.min_; + if (other.max_ > max_) max_ = other.max_; + num_ += other.num_; + sum_ += other.sum_; + sum_squares_ += other.sum_squares_; + for (int b = 0; b < kNumBuckets; b++) { + buckets_[b] += other.buckets_[b]; + } +} + +double Histogram::Median() const { return Percentile(50.0); } + +double Histogram::Percentile(double p) const { + double threshold = num_ * (p / 100.0); + double sum = 0; + for (int b = 0; b < kNumBuckets; b++) { + sum += buckets_[b]; + if (sum >= threshold) { + // Scale linearly within this bucket + double left_point = (b == 0) ? 0 : kBucketLimit[b - 1]; + double right_point = kBucketLimit[b]; + double left_sum = sum - buckets_[b]; + double right_sum = sum; + double pos = (threshold - left_sum) / (right_sum - left_sum); + double r = left_point + (right_point - left_point) * pos; + if (r < min_) r = min_; + if (r > max_) r = max_; + return r; + } + } + return max_; +} + +double Histogram::Average() const { + if (num_ == 0.0) return 0; + return sum_ / num_; +} + +double Histogram::StandardDeviation() const { + if (num_ == 0.0) return 0; + double variance = (sum_squares_ * num_ - sum_ * sum_) / (num_ * num_); + return sqrt(variance); +} + +std::string Histogram::ToString() const { + std::string r; + char buf[200]; + std::snprintf(buf, sizeof(buf), "Count: %.0f Average: %.4f StdDev: %.2f\n", + num_, Average(), StandardDeviation()); + r.append(buf); + std::snprintf(buf, sizeof(buf), "Min: %.4f Median: %.4f Max: %.4f\n", + (num_ == 0.0 ? 0.0 : min_), Median(), max_); + r.append(buf); + r.append("------------------------------------------------------\n"); + const double mult = 100.0 / num_; + double sum = 0; + for (int b = 0; b < kNumBuckets; b++) { + if (buckets_[b] <= 0.0) continue; + sum += buckets_[b]; + std::snprintf(buf, sizeof(buf), "[ %7.0f, %7.0f ) %7.0f %7.3f%% %7.3f%% ", + ((b == 0) ? 0.0 : kBucketLimit[b - 1]), // left + kBucketLimit[b], // right + buckets_[b], // count + mult * buckets_[b], // percentage + mult * sum); // cumulative percentage + r.append(buf); + + // Add hash marks based on percentage; 20 marks for 100%. + int marks = static_cast<int>(20 * (buckets_[b] / num_) + 0.5); + r.append(marks, '#'); + r.push_back('\n'); + } + return r; +} + +} // namespace leveldb |