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60 lines
1.9 KiB
C++
60 lines
1.9 KiB
C++
// Copyright 2016 The Chromium Authors. All rights reserved.
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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#ifndef NET_BASE_PERCENTILE_ESTIMATOR_H_
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#define NET_BASE_PERCENTILE_ESTIMATOR_H_
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#include "base/callback.h"
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#include "base/macros.h"
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#include "net/base/net_export.h"
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namespace net {
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// This class estimates statistical percentiles (e.g. 10%l, 50%l) for
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// integer distributions presented in stream form. These estimates
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// adjust automatically when the stream distribution changes.
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// TODO(rdsmith): Expand the class to maintain floating point
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// estimates rather than integer estimates, when there's a use case
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// for that that deserves the extra complexity and pitfalls of
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// floating point arithmetic.
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class NET_EXPORT PercentileEstimator {
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public:
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using RandomNumberCallback = base::Callback<int(void)>;
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static const int kMedianPercentile = 50;
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// |percentile| is a number between 0 and 100 indicating what percentile
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// should be estimated (e.g. 50 would be a median estimate).
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// |initial_estimate| is the value the class is seeded with; in other
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// words, if AddSample() is never called,
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// |CurrentEstimate() == initial_estimate|.
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PercentileEstimator(int percentile, int initial_estimate);
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~PercentileEstimator();
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int current_estimate() const { return current_estimate_; }
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void AddSample(int sample);
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// Specify a callback that will generate a "random" number
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// in the range [0,99] on each call. Used so that tests can
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// rely on reproducible behavior.
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void SetRandomNumberGeneratorForTesting(
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RandomNumberCallback generator_callback);
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private:
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const int percentile_;
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bool sign_positive_;
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int current_estimate_;
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int current_step_;
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RandomNumberCallback generator_callback_;
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DISALLOW_COPY_AND_ASSIGN(PercentileEstimator);
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};
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} // namespace net
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#endif // NET_BASE_PERCENTILE_ESTIMATOR_H_
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