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31 lines
839 B
31 lines
839 B
package brotli
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/* Copyright 2013 Google Inc. All Rights Reserved.
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Distributed under MIT license.
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See file LICENSE for detail or copy at https://opensource.org/licenses/MIT
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*/
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/* Functions for clustering similar histograms together. */
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type histogramPair struct {
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idx1 uint32
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idx2 uint32
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cost_combo float64
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cost_diff float64
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}
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func histogramPairIsLess(p1 *histogramPair, p2 *histogramPair) bool {
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if p1.cost_diff != p2.cost_diff {
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return p1.cost_diff > p2.cost_diff
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}
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return (p1.idx2 - p1.idx1) > (p2.idx2 - p2.idx1)
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}
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/* Returns entropy reduction of the context map when we combine two clusters. */
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func clusterCostDiff(size_a uint, size_b uint) float64 {
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var size_c uint = size_a + size_b
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return float64(size_a)*fastLog2(size_a) + float64(size_b)*fastLog2(size_b) - float64(size_c)*fastLog2(size_c)
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}
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