75 lines
2.3 KiB
C#
75 lines
2.3 KiB
C#
/*
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* Copyright 2016 The Cartographer Authors
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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namespace CartographerSharp.Common;
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/// <summary>
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/// Signals when a sample should be taken from a stream of data to select a
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/// uniformly distributed fraction of the data.
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/// </summary>
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public class FixedRatioSampler
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{
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/// <summary>
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/// Sampling occurs if the proportion of samples to pulses drops below this number.
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/// </summary>
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private readonly double _ratio;
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private long _numPulses = 0;
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private long _numSamples = 0;
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/// <summary>
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/// Creates a fixed ratio sampler with the given ratio.
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/// </summary>
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/// <param name="ratio">Ratio between 0.0 and 1.0. Sampling occurs if the proportion of samples to pulses drops below this number.</param>
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public FixedRatioSampler(double ratio)
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{
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if (ratio < 0.0 || ratio > 1.0)
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{
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throw new ArgumentException($"Ratio must be between 0.0 and 1.0, got {ratio}", nameof(ratio));
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}
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if (ratio == 0.0)
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{
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// Warning: FixedRatioSampler is dropping all data
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}
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_ratio = ratio;
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}
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/// <summary>
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/// Returns true if this pulse should result in a sample.
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/// </summary>
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public bool Pulse()
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{
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_numPulses++;
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if (_numSamples / _numPulses < _ratio)
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{
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_numSamples++;
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return true;
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}
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return false;
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}
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/// <summary>
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/// Returns a debug string describing the current ratio of samples to pulses.
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/// </summary>
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public string DebugString()
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{
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var percentage = _numPulses > 0 ? 100.0 * _numSamples / _numPulses : 0.0;
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return $"{_numSamples} ({percentage:F2}%)";
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}
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}
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