From 0144471d0fbb5597018c0faf008e1fa205591d54 Mon Sep 17 00:00:00 2001
From: Tomasz Lelek <tomekl007@gmail.com>
Date: Sun, 18 Jun 2017 03:35:33 +0200
Subject: [PATCH] BAEL-980 lsh code (#2047)

* BAEL-980 lsh code

* BAEL-980 rename test
---
 libraries/pom.xml                             |  7 +++
 .../lsh/LocalSensitiveHashingUnitTest.java    | 48 +++++++++++++++++++
 2 files changed, 55 insertions(+)
 create mode 100644 libraries/src/test/java/com/baeldung/lsh/LocalSensitiveHashingUnitTest.java

diff --git a/libraries/pom.xml b/libraries/pom.xml
index da040c9731..12511a243a 100644
--- a/libraries/pom.xml
+++ b/libraries/pom.xml
@@ -345,6 +345,12 @@
             <artifactId>opennlp-tools</artifactId>
             <version>1.8.0</version>
         </dependency>
+        <dependency>
+            <groupId>info.debatty</groupId>
+            <artifactId>java-lsh</artifactId>
+            <version>${java-lsh.version}</version>
+        </dependency>
+
 
     </dependencies>
     <properties>
@@ -371,6 +377,7 @@
         <serenity.plugin.version>1.4.0</serenity.plugin.version>
         <jUnitParams.version>1.1.0</jUnitParams.version>
         <netty.version>4.1.10.Final</netty.version>
+        <java-lsh.version>0.10</java-lsh.version>
     </properties>
 
 </project>
\ No newline at end of file
diff --git a/libraries/src/test/java/com/baeldung/lsh/LocalSensitiveHashingUnitTest.java b/libraries/src/test/java/com/baeldung/lsh/LocalSensitiveHashingUnitTest.java
new file mode 100644
index 0000000000..fbcda2a70d
--- /dev/null
+++ b/libraries/src/test/java/com/baeldung/lsh/LocalSensitiveHashingUnitTest.java
@@ -0,0 +1,48 @@
+package com.baeldung.lsh;
+
+import info.debatty.java.lsh.LSHMinHash;
+import org.junit.Ignore;
+import org.junit.Test;
+
+import java.util.Arrays;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+
+public class LocalSensitiveHashingUnitTest {
+
+    @Ignore("for simplicity of the example number of input vectors is very low, that's why LSH may yield non deterministic results")
+    @Test()
+    public void givenNVectors_whenPerformLSH_thenShouldCalculateSameHashForSimilarVectors() {
+        //given
+        boolean[] vector1 = new boolean[]{true, true, true, true, true};
+        boolean[] vector2 = new boolean[]{false, false, false, true, false};
+        boolean[] vector3 = new boolean[]{false, false, true, true, false};
+
+        int sizeOfVectors = 5;
+        int numberOfBuckets = 10;
+        int stages = 4;
+
+        LSHMinHash lsh = new LSHMinHash(stages, numberOfBuckets, sizeOfVectors);
+
+        //when
+        int[] firstHash = lsh.hash(vector1);
+        int[] secondHash = lsh.hash(vector2);
+        int[] thirdHash = lsh.hash(vector3);
+
+        System.out.println(Arrays.toString(firstHash));
+        System.out.println(Arrays.toString(secondHash));
+        System.out.println(Arrays.toString(thirdHash));
+
+        //then
+        int lastIndexOfResult = stages - 1;
+        assertThat(firstHash[lastIndexOfResult]).isNotEqualTo(secondHash[lastIndexOfResult]);
+        assertThat(firstHash[lastIndexOfResult]).isNotEqualTo(thirdHash[lastIndexOfResult]);
+        assertThat(isCloseOrEqual(secondHash[lastIndexOfResult], thirdHash[lastIndexOfResult], numberOfBuckets)).isTrue();
+    }
+
+    private boolean isCloseOrEqual(int secondHash, int thirdHash, int numberOfBuckets) {
+        return Math.abs(secondHash - thirdHash) < numberOfBuckets / 2;
+    }
+}
+