@Override
        public boolean terminate(final Memory memory) {
            assertTrue(memory.exists("m1"));
            assertTrue(memory.exists("m2"));
            assertTrue(memory.exists("m3"));
            assertTrue(memory.exists("m4"));
            if (memory.isInitialIteration()) {
                assertFalse(memory.get("m1"));
                assertTrue(memory.get("m2"));
                assertEquals(6l, memory.<Long>get("m3").longValue());
                assertEquals(-6, memory.<Integer>get("m4").intValue());
                return false;
            } else {
                assertTrue(memory.get("m1"));
                assertTrue(memory.get("m2"));
                assertEquals(18l, memory.<Long>get("m3").longValue());
                assertEquals(-18, memory.<Integer>get("m4").intValue());
                return true;
            }
        }
Javadoc for {@code ConcurrentSkipListSet} includes this little note: "Beware that, unlike in most
collections, the size method is not a constant-time operation." Doing a traversal of elements will yield
the correct count. Java 11 upgrade seemed to force this failure consistently.
gremlin-test/src/main/java/org/apache/tinkerpop/gremlin/process/computer/GraphComputerTest.java