Added support methods for spark k-nn graph building

Author: tdebatty

src/main/java/info/debatty/java/stringsimilarity/StringProfile.java

@@ -51,7 +51,7 @@ public double cosineSimilarity(StringProfile other) throws Exception {
             throw new Exception("Profiles were not created using the same kshingling object!");
         }
 
-        return this.vector.dotProduct(other.vector) / (this.vector.norm() * other.vector.norm());
+        return this.vector.cosineSimilarity(other.vector);
     }
 
     /**

src/main/java/info/debatty/java/utils/SparseBooleanVector.java

@@ -24,6 +24,7 @@
 
 package info.debatty.java.utils;
 
+import java.io.Serializable;
 import java.util.HashMap;
 import java.util.SortedSet;
 import java.util.TreeSet;
@@ -32,7 +33,7 @@
  *
  * @author tibo
  */
-public class SparseBooleanVector {
+public class SparseBooleanVector implements Serializable {
 
     /** 
      * Indicates the positions that hold the value "true"

src/main/java/info/debatty/java/utils/SparseIntegerVector.java

@@ -24,6 +24,7 @@
 
 package info.debatty.java.utils;
 
+import java.io.Serializable;
 import java.util.HashMap;
 import java.util.SortedSet;
 import java.util.TreeSet;
@@ -32,7 +33,7 @@
  * Sparse vector of int, implemented using two arrays
  * @author Thibault Debatty
  */
-public class SparseIntegerVector {
+public class SparseIntegerVector implements Serializable {
 
     protected int[] keys;
     protected int[] values;
@@ -81,6 +82,29 @@ public SparseIntegerVector(int[] array) {
         }
     }
 
+    public double cosineSimilarity(SparseIntegerVector other) {
+        double den = this.norm() * other.norm();
+        double agg = 0;
+        int i = 0;
+        int j = 0;
+        while (i < this.keys.length  && j < other.keys.length) {
+            int k1 = this.keys[i];
+            int k2 = other.keys[j];
+
+            if (k1 == k2) {
+                agg += this.values[i] * other.values[j] / den;
+                i++;
+                j++;
+
+            } else if (k1 < k2) {
+                i++;
+            } else {
+                j++;
+            }
+        }
+        return agg;
+    }
+    
     /**
      * 
      * @param other

src/test/java/info/debatty/java/utils/SparseIntegerVectorTest.java

@@ -81,6 +81,20 @@ public void testDotProduct_doubleArr() {
         double result = instance.dotProduct(other);
         assertEquals(expResult, result, 0.0);
     }
+    
+    
+    /**
+     * Test of cosineSimilarity method, of class SparseIntegerVector.
+     */
+    @Test
+    public void testCosineSimilarity() {
+        System.out.println("cosineSimilarity");
+        SparseIntegerVector other = new SparseIntegerVector(new int[]{0, 1, 2, 3});
+        SparseIntegerVector instance = new SparseIntegerVector(new int[]{1, 2, 0, 0});
+        double expResult = instance.dotProduct(other) / (instance.norm() * other.norm());
+        double result = instance.cosineSimilarity(other);
+        assertEquals(expResult, result, 0.0);
+    }
 
     /**
      * Test of norm method, of class SparseIntegerVector.