Fix: Handle GroupQueueCallbacks to Avoid Miscounts

Author: janniklinde

src/main/java/org/apache/sysds/runtime/ooc/stream/MergedOOCStream.java

@@ -85,6 +85,17 @@ public MergedOOCStream(List<OOCStream<T>> sources) {
 						if(_failed.get())
 							return;
 
+						if(cb instanceof OOCStream.GroupQueueCallback<?>) {
+							OOCStream.GroupQueueCallback<T> group = (OOCStream.GroupQueueCallback<T>) cb;
+							for(int i = 0; i < group.size(); i++) {
+								OOCStream.QueueCallback<T> sub = group.getCallback(i);
+								try(sub) {
+									_taskQueue.enqueue(sub.keepOpen());
+								}
+							}
+							return;
+						}
+
 						_taskQueue.enqueue(cb.keepOpen());
 					}
 				}

src/test/java/org/apache/sysds/test/functions/ooc/CBindTest.java

@@ -54,8 +54,7 @@ public void setUp() {
 	@Test
 	public void testCBindAppendBlock() { runCBindTest(1000, 1000, 1000, 1000);}
 
-	// TODO: fix OOC internals
-	// @Test
+	@Test
 	public void testCBindAppendBlockTwoLeftBlocks() {runCBindTest(1000, 2000, 1000, 1000);}
 
 	@Test