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Diffstat (limited to 'util/histogram.cc')
| -rw-r--r-- | util/histogram.cc | 139 |
1 files changed, 139 insertions, 0 deletions
diff --git a/util/histogram.cc b/util/histogram.cc new file mode 100644 index 0000000..bb95f58 --- /dev/null +++ b/util/histogram.cc @@ -0,0 +1,139 @@ +// 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 <math.h> +#include <stdio.h> +#include "port/port.h" +#include "util/histogram.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]; + snprintf(buf, sizeof(buf), + "Count: %.0f Average: %.4f StdDev: %.2f\n", + num_, Average(), StandardDeviation()); + r.append(buf); + 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]; + 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 |