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