Merge remote-tracking branch 'origin/feat-improve-compression-ratio' …

…into feat-improve-compression-ratio

# Conflicts:
#	src/main/java/game/Encoder.java
#	src/main/java/game/codec/BinarySearch.java
#	src/main/java/game/codec/Rans.java
#	src/main/java/game/codec/RansConfiguration.java
#	src/main/java/game/codec/RansDecoder.java
#	src/main/java/game/codec/RansEncoder.java

src/main/java/game/Encoder.java

@@ -4,10 +4,6 @@
 import org.lichess.compression.BitWriter;
 import org.lichess.compression.game.codec.Rans;
 
-import java.util.Arrays;
-import java.util.regex.Matcher;
-import java.util.regex.Pattern;
-
 public class Encoder {
  private final Rans rans = new Rans();
 

src/main/java/game/codec/Histogram.java

@@ -0,0 +1,34 @@
+package org.lichess.compression.game.entropycoding;
+
+public class Histogram {
+ private final int[] cdf;
+
+ public Histogram(int[] frequencies) {
+ this.cdf = computeCdf(frequencies);
+ }
+
+ private static int[] computeCdf(int[] frequencies) {
+ int[] cdf = new int[frequencies.length + 1];
+ cdf[0] = 0;
+ for (int i = 1; i < cdf.length; i++) {
+ cdf[i] = cdf[i - 1] + frequencies[i - 1];
+ }
+ return cdf;
+ }
+
+ public int getFrequencyAt(int i) {
+ return cdf[i + 1] - cdf[i];
+ }
+
+ public int getCdfAt(int i) {
+ return cdf[i];
+ }
+
+ public int getQuantileFunction(int frequency) {
+ return BinarySearch.search(cdf, frequency);
+ }
+
+ public int getNumberOfBins() {
+ return cdf.length - 1;
+ }
+}