Fix the dropping in OM2 as per Arun

Author: manolama

src/main/java/com/yahoo/egads/models/tsmm/OlympicModel2.java

@@ -201,6 +201,27 @@ public WeightedValue(final double value, final int weight) {
         public int compareTo(final WeightedValue other) {
             return Double.compare(value, other.value);
         }
+    
+        /**
+         * Drops as many of the highest or lowest values as possible, leaving
+         * at least one value in the list.
+         * @param accumulator A non-null accumulator list.
+         * @param count A count of 1 or more.
+         * @param highest Drop higher values == true or drop lower values == false.
+         */
+        public static void drop(final List<WeightedValue> accumulator, 
+                final int count, final boolean highest) {
+            for (int x = 0; x < count; x++) {
+                if (accumulator.size() <= 1) {
+                    break;
+                }
+                if (highest) {
+                    accumulator.remove(Collections.max(accumulator));
+                } else {
+                    accumulator.remove(Collections.min(accumulator));
+                }
+            }
+        }
     }
 
     @Override
@@ -254,13 +275,13 @@ public void train(final DataSequence data) throws Exception {
                 }
             }
 
-            if ((drop_lowest > 0 || drop_highest > 0)
-                    && accumulator.size() > (drop_lowest + drop_highest)) {
-                for (int x = 0; x < drop_lowest; x++) {
-                    accumulator.remove(Collections.min(accumulator));
-                }
-                for (int x = 0; x < drop_highest; x++) {
-                    accumulator.remove(Collections.max(accumulator));
+            if (drop_lowest > 0 || drop_highest > 0) {
+                if (drop_highest > drop_lowest) {
+                    WeightedValue.drop(accumulator, drop_highest, true);
+                    WeightedValue.drop(accumulator, drop_lowest, false);
+                } else {
+                    WeightedValue.drop(accumulator, drop_lowest, false);
+                    WeightedValue.drop(accumulator, drop_highest, true);
                 }
             }
 

src/test/java/com/yahoo/egads/models/tsmm/TestOlympicModel2.java

@@ -1051,7 +1051,7 @@ public void trainDrop() throws Exception {
         assertEquals(1477872300, (long) model.model.get(1).getKey());
         assertEquals(50.0, model.model.get(1).getValue(), 0.00001);
 
-        // two each - TOO MANY so we don't drop any
+        // two each - TOO MANY so we drop as much as possible
         config.setProperty("NUM_TO_DROP_HIGHEST", "2");
         config.setProperty("NUM_TO_DROP_LOWEST", "2");
         model = new OlympicModel2(config);
@@ -1072,11 +1072,11 @@ public void trainDrop() throws Exception {
 
         assertEquals(2, model.model.size());
         assertEquals(1477872000, (long) model.model.get(0).getKey());
-        assertEquals(25.0, model.model.get(0).getValue(), 0.00001);
+        assertEquals(30.0, model.model.get(0).getValue(), 0.00001);
         assertEquals(1477872300, (long) model.model.get(1).getKey());
-        assertEquals(47.5, model.model.get(1).getValue(), 0.00001);
+        assertEquals(55.0, model.model.get(1).getValue(), 0.00001);
 
-        // one each - TOO MANY with NaNs so we don't drop any
+        // one each - TOO MANY so we drop as much as possible
         config.setProperty("NUM_TO_DROP_HIGHEST", "1");
         config.setProperty("NUM_TO_DROP_LOWEST", "1");
         model = new OlympicModel2(config);
@@ -1097,9 +1097,9 @@ public void trainDrop() throws Exception {
 
         assertEquals(2, model.model.size());
         assertEquals(1477872000, (long) model.model.get(0).getKey());
-        assertEquals(25.0, model.model.get(0).getValue(), 0.00001);
+        assertEquals(40.0, model.model.get(0).getValue(), 0.00001);
         assertEquals(1477872300, (long) model.model.get(1).getKey());
-        assertEquals(45.0, model.model.get(1).getValue(), 0.00001);
+        assertEquals(65.0, model.model.get(1).getValue(), 0.00001);
     }
 
     @Test