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A Fibonacci fitter is useful in situations where you want more precision on the low end than an ExponentialFitter with exponent base 2 provides without the hassle of dealing with non-integer boundaries, such as would be created by an exponential fitter with a base of less than 2. Fibonacci fitters are ideal for integer metrics that are bounded across a certain range, e.g. integers between 1 and 1,000. This also cleans up some unit test comments. ------------- Created by MOE: https://github.com/google/moe MOE_MIGRATED_REVID=156773367
64 lines
2.4 KiB
Java
64 lines
2.4 KiB
Java
// Copyright 2017 The Nomulus Authors. All Rights Reserved.
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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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package google.registry.monitoring.metrics;
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import static com.google.common.base.Preconditions.checkArgument;
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import com.google.auto.value.AutoValue;
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import com.google.common.collect.ImmutableSortedSet;
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/**
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* A {@link DistributionFitter} with intervals of increasing size using the Fibonacci sequence.
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*
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* <p>A Fibonacci fitter is useful in situations where you want more precision on the low end than
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* an {@link ExponentialFitter} with exponent base 2 would provide without the hassle of dealing
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* with non-integer boundaries, such as would be created by an exponential fitter with a base of
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* less than 2. Fibonacci fitters are ideal for integer metrics that are bounded across a certain
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* range, e.g. integers between 1 and 1,000.
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*
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* <p>The interval boundaries are chosen as {@code (-inf, 0), [0, 1), [1, 2), [2, 3), [3, 5), [5,
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* 8), [8, 13)}, etc., up to {@code [fibonacciFloor(maxBucketSize), inf)}.
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*/
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@AutoValue
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public abstract class FibonacciFitter implements DistributionFitter {
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/**
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* Returns a new {@link FibonacciFitter}.
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*
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* @param maxBucketSize the maximum bucket size to create (rounded down to the nearest Fibonacci
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* number)
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* @throws IllegalArgumentException if {@code maxBucketSize <= 0}
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*/
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public static FibonacciFitter create(long maxBucketSize) {
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checkArgument(maxBucketSize > 0, "maxBucketSize must be greater than 0");
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ImmutableSortedSet.Builder<Double> boundaries = ImmutableSortedSet.naturalOrder();
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boundaries.add(Double.valueOf(0));
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long i = 1;
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long j = 2;
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long k = 3;
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while (i <= maxBucketSize) {
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boundaries.add(Double.valueOf(i));
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i = j;
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j = k;
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k = i + j;
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}
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return new AutoValue_FibonacciFitter(boundaries.build());
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}
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@Override
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public abstract ImmutableSortedSet<Double> boundaries();
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}
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