| 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) |
| } |