Adding sbd method (#23)

Adding SBD method and its test.

Author: avilchess

src/main/java/io/shapelets/khiva/Distances.java

@@ -22,6 +22,8 @@ public class Distances extends Library {
 
     private native static long[] manhattan(long ref);
 
+    private native static long[] sbd(long ref);
+
     private native static long[] squaredEuclidean(long ref);
 
 
@@ -69,6 +71,22 @@ public static Array hamming(Array tss) {
         return new Array(refs[1]);
     }
 
+    /**
+     * Calculates the Shape-Based distance (SBD). It computes the normalized cross-correlation and it returns 1.0
+     * minus the value that maximizes the correlation value between each pair of time series.
+     *
+     * @param tss Expects an input array whose dimension zero is the length of the time series (all the same) and
+     *            dimension one indicates the number of time series.
+     * @return Array with an upper triangular matrix where each position corresponds to the distance between two
+     * time series. Diagonal elements will be zero. For example: Position row 0 column 1 records the distance between time
+     * series 0 and time series 1.
+     */
+    public static Array sbd(Array tss) {
+        long[] refs = sbd(tss.getReference());
+        tss.setReference(refs[0]);
+        return new Array(refs[1]);
+    }
+
     /**
      * Calculates Manhattan distances between time series.
      *

src/test/java/io/shapelets/khiva/DistancesTest.java

@@ -43,27 +43,6 @@ public void testEuclidean() throws Exception {
         }
     }
 
-    @Test
-    public void testSquaredEuclidean() throws Exception {
-        float[] timeSeries = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
-        long[] dims = {4, 3, 1, 1};
-        try (
-                Array arrayOfTimeSeries = new Array(timeSeries, dims);
-                Array b = Distances.squaredEuclidean(arrayOfTimeSeries)
-        ) {
-            float[] result = b.getData();
-            Assert.assertEquals(result[0], 0, DELTA);
-            Assert.assertEquals(result[1], 0, DELTA);
-            Assert.assertEquals(result[2], 0, DELTA);
-            Assert.assertEquals(result[3], 64, DELTA);
-            Assert.assertEquals(result[4], 0, DELTA);
-            Assert.assertEquals(result[5], 0, DELTA);
-            Assert.assertEquals(result[6], 256, DELTA);
-            Assert.assertEquals(result[7], 64, DELTA);
-            Assert.assertEquals(result[8], 0, DELTA);
-        }
-    }
-
     @Test
     public void testDwt() throws Exception {
         float[] timeSeries = {1, 1, 1, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5};
@@ -114,4 +93,42 @@ public void testManhattan() throws Exception {
             }
         }
     }
+
+    @Test
+    public void testSBD() throws Exception {
+        float[] timeSeries = {1, 2, 3, 4, 5, 1, 1, 0, 1, 1, 10, 12, 0, 0, 1};
+        long[] dims = {5, 3, 1, 1};
+        try (
+                Array a = new Array(timeSeries, dims);
+                Array b = Distances.sbd(a)
+        ) {
+            float[] result = b.getData();
+            float[] expectedResult = {0, 0, 0, 0.505025f, 0, 0, 0.458583f, 0.564093f, 0};
+            Assert.assertEquals(expectedResult.length, result.length, DELTA);
+            for (int i = 0; i < result.length; i++) {
+                Assert.assertEquals(expectedResult[i], result[i], DELTA);
+            }
+        }
+    }
+
+    @Test
+    public void testSquaredEuclidean() throws Exception {
+        float[] timeSeries = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11};
+        long[] dims = {4, 3, 1, 1};
+        try (
+                Array arrayOfTimeSeries = new Array(timeSeries, dims);
+                Array b = Distances.squaredEuclidean(arrayOfTimeSeries)
+        ) {
+            float[] result = b.getData();
+            Assert.assertEquals(result[0], 0, DELTA);
+            Assert.assertEquals(result[1], 0, DELTA);
+            Assert.assertEquals(result[2], 0, DELTA);
+            Assert.assertEquals(result[3], 64, DELTA);
+            Assert.assertEquals(result[4], 0, DELTA);
+            Assert.assertEquals(result[5], 0, DELTA);
+            Assert.assertEquals(result[6], 256, DELTA);
+            Assert.assertEquals(result[7], 64, DELTA);
+            Assert.assertEquals(result[8], 0, DELTA);
+        }
+    }
 }