statistical encoding

brouter-codec/src/test/java/btools/codec/StatCoderContextTest.java

@@ -0,0 +1,127 @@
+package btools.codec;
+
+import java.util.Arrays;
+import java.util.Random;
+
+import org.junit.Assert;
+import org.junit.Test;
+
+public class StatCoderContextTest
+{
+  @Test
+  public void noisyVarBitsEncodeDecodeTest()
+  {
+    byte[] ab = new byte[40000];
+    StatCoderContext ctx = new StatCoderContext( ab );
+    for ( int noisybits = 0; noisybits < 12; noisybits++ )
+    {
+      for ( int i = 0; i < 1000; i++ )
+      {
+        ctx.encodeNoisyNumber( i, noisybits );
+      }
+    }
+    ctx = new StatCoderContext( ab );
+
+    for ( int noisybits = 0; noisybits < 12; noisybits++ )
+    {
+      for ( int i = 0; i < 1000; i++ )
+      {
+        int value = ctx.decodeNoisyNumber( noisybits );
+        if ( value != i )
+        {
+          Assert.fail( "value mismatch: noisybits=" + noisybits + " i=" + i + " value=" + value );
+        }
+      }
+    }
+  }
+
+  @Test
+  public void noisySignedVarBitsEncodeDecodeTest()
+  {
+    byte[] ab = new byte[80000];
+    StatCoderContext ctx = new StatCoderContext( ab );
+    for ( int noisybits = 0; noisybits < 12; noisybits++ )
+    {
+      for ( int i = -1000; i < 1000; i++ )
+      {
+        ctx.encodeNoisyDiff( i, noisybits );
+      }
+    }
+    ctx = new StatCoderContext( ab );
+
+    for ( int noisybits = 0; noisybits < 12; noisybits++ )
+    {
+      for ( int i = -1000; i < 1000; i++ )
+      {
+        int value = ctx.decodeNoisyDiff( noisybits );
+        if ( value != i )
+        {
+          Assert.fail( "value mismatch: noisybits=" + noisybits + " i=" + i + " value=" + value );
+        }
+      }
+    }
+  }
+
+  @Test
+  public void predictedValueEncodeDecodeTest()
+  {
+    byte[] ab = new byte[80000];
+    StatCoderContext ctx = new StatCoderContext( ab );
+    for ( int value = -100; value < 100; value += 5 )
+    {
+      for ( int predictor = -200; predictor < 200; predictor += 7 )
+      {
+        ctx.encodePredictedValue( value, predictor );
+      }
+    }
+    ctx = new StatCoderContext( ab );
+
+    for ( int value = -100; value < 100; value += 5 )
+    {
+      for ( int predictor = -200; predictor < 200; predictor += 7 )
+      {
+        int decodedValue = ctx.decodePredictedValue( predictor );
+        if ( value != decodedValue )
+        {
+          Assert.fail( "value mismatch: value=" + value + " predictor=" + predictor + " decodedValue=" + decodedValue );
+        }
+      }
+    }
+  }
+
+  @Test
+  public void sortedArrayEncodeDecodeTest()
+  {
+    Random rand = new Random();
+    int size = 1000000;
+    int[] values = new int[size];
+    for ( int i = 0; i < size; i++ )
+    {
+      values[i] = rand.nextInt() & 0x0fffffff;
+    }
+    values[5] = 175384; // force collision
+    values[8] = 175384;
+
+    values[15] = 275384; // force neighbours
+    values[18] = 275385;
+
+    Arrays.sort( values );
+
+    byte[] ab = new byte[3000000];
+    StatCoderContext ctx = new StatCoderContext( ab );
+    ctx.encodeSortedArray( values, 0, size, 0x08000000, 0 );
+
+    ctx = new StatCoderContext( ab );
+
+    int[] decodedValues = new int[size];
+    ctx.decodeSortedArray( decodedValues, 0, size, 0x08000000, 0 );
+
+    for ( int i = 0; i < size; i++ )
+    {
+      if ( values[i] != decodedValues[i] )
+      {
+        Assert.fail( "mismatch at i=" + i + " " + values[i] + "<>" + decodedValues[i] );
+      }
+    }
+  }
+}