pylucene 3.5.0-3

[pylucene.git] / lucene-java-3.5.0 / lucene / contrib / spellchecker / src / java / org / apache / lucene / search / spell / JaroWinklerDistance.java

diff --git a/lucene-java-3.5.0/lucene/contrib/spellchecker/src/java/org/apache/lucene/search/spell/JaroWinklerDistance.java b/lucene-java-3.5.0/lucene/contrib/spellchecker/src/java/org/apache/lucene/search/spell/JaroWinklerDistance.java
new file mode 100644 (file)
index 0000000..3818173
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+++ b/lucene-java-3.5.0/lucene/contrib/spellchecker/src/java/org/apache/lucene/search/spell/JaroWinklerDistance.java
@@ -0,0 +1,112 @@
+package org.apache.lucene.search.spell;
+
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import java.util.Arrays;
+
+public class JaroWinklerDistance implements StringDistance {
+
+  private float threshold = 0.7f;
+
+  private int[] matches(String s1, String s2) {
+    String max, min;
+    if (s1.length() > s2.length()) {
+      max = s1;
+      min = s2;
+    } else {
+      max = s2;
+      min = s1;
+    }
+    int range = Math.max(max.length() / 2 - 1, 0);
+    int[] matchIndexes = new int[min.length()];
+    Arrays.fill(matchIndexes, -1);
+    boolean[] matchFlags = new boolean[max.length()];
+    int matches = 0;
+    for (int mi = 0; mi < min.length(); mi++) {
+      char c1 = min.charAt(mi);
+      for (int xi = Math.max(mi - range, 0), xn = Math.min(mi + range + 1, max
+          .length()); xi < xn; xi++) {
+        if (!matchFlags[xi] && c1 == max.charAt(xi)) {
+          matchIndexes[mi] = xi;
+          matchFlags[xi] = true;
+          matches++;
+          break;
+        }
+      }
+    }
+    char[] ms1 = new char[matches];
+    char[] ms2 = new char[matches];
+    for (int i = 0, si = 0; i < min.length(); i++) {
+      if (matchIndexes[i] != -1) {
+        ms1[si] = min.charAt(i);
+        si++;
+      }
+    }
+    for (int i = 0, si = 0; i < max.length(); i++) {
+      if (matchFlags[i]) {
+        ms2[si] = max.charAt(i);
+        si++;
+      }
+    }
+    int transpositions = 0;
+    for (int mi = 0; mi < ms1.length; mi++) {
+      if (ms1[mi] != ms2[mi]) {
+        transpositions++;
+      }
+    }
+    int prefix = 0;
+    for (int mi = 0; mi < min.length(); mi++) {
+      if (s1.charAt(mi) == s2.charAt(mi)) {
+        prefix++;
+      } else {
+        break;
+      }
+    }
+    return new int[] { matches, transpositions / 2, prefix, max.length() };
+  }
+
+  public float getDistance(String s1, String s2) {
+    int[] mtp = matches(s1, s2);
+    float m = mtp[0];
+    if (m == 0) {
+      return 0f;
+    }
+    float j = ((m / s1.length() + m / s2.length() + (m - mtp[1]) / m)) / 3;
+    float jw = j < getThreshold() ? j : j + Math.min(0.1f, 1f / mtp[3]) * mtp[2]
+        * (1 - j);
+    return jw;
+  }
+
+  /**
+   * Sets the threshold used to determine when Winkler bonus should be used.
+   * Set to a negative value to get the Jaro distance.
+   * @param threshold the new value of the threshold
+   */
+  public void setThreshold(float threshold) {
+    this.threshold = threshold;
+  }
+
+  /**
+   * Returns the current value of the threshold used for adding the Winkler bonus.
+   * The default value is 0.7.
+   * @return the current value of the threshold
+   */
+  public float getThreshold() {
+    return threshold;
+  }
+}