App.java

import org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.GraphTraversalSource;
import org.apache.tinkerpop.gremlin.structure.Graph;
import org.apache.tinkerpop.gremlin.structure.Vertex;
import org.apache.tinkerpop.gremlin.tinkergraph.structure.TinkerGraph;

import java.util.Arrays;
import java.util.List;
import java.util.Map;
import java.util.function.BinaryOperator;

import static org.apache.tinkerpop.gremlin.process.traversal.Operator.assign;
import static org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.__.hasLabel;
import static org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.__.out;
import static org.apache.tinkerpop.gremlin.process.traversal.dsl.graph.__.sack;
import static org.apache.tinkerpop.gremlin.structure.T.id;
import static org.apache.tinkerpop.gremlin.structure.T.label;

/**
 * @author Daniel Kuppitz (http://gremlin.guru)
 */
public class App {

    // https://groups.google.com/d/msgid/gremlin-users/04bed1f5-fe6a-42c3-9317-dc3250f3474d%40googlegroups.com
    public static void main(final String[] args) {

        final Graph graph = TinkerGraph.open();
        final GraphTraversalSource g = graph.traversal();
        final Vertex v1 = graph.addVertex(id, 1, label, "ABC", "alive", "yes", "Val", new double[]{10f, 15f});
        final Vertex v5 = graph.addVertex(id, 5, label, "notABC", "alive", "yes", "Val", new double[]{1f, 3f, 6f, 9f});
        final Vertex v6 = graph.addVertex(id, 6, label, "notABC", "alive", "yes", "Val", new double[]{5f, 2f});
        final Vertex v7 = graph.addVertex(id, 7, label, "notABC", "alive", "no", "Val", new double[]{1f, 7f});
        final Vertex v10 = graph.addVertex(id, 10, label, "XZ", "alive", "yes", "Val", new double[]{1f, 8f});
        final Vertex v11 = graph.addVertex(id, 11, label, "XZ", "alive", "yes", "Val", new double[]{3f, 4f});
        final Vertex v12 = graph.addVertex(id, 12, label, "XZ", "alive", "yes", "Val", new double[]{1f, 5f});
        final Vertex v13 = graph.addVertex(id, 13, label, "XZ", "alive", "yes", "Val", new double[]{1f, 9f});
        
        v1.addEdge("flows", v5, id, 21);
        v5.addEdge("flows", v6, id, 22);
        v5.addEdge("flows", v7, id, 23);
        v6.addEdge("flows", v10, id, 24);
        v6.addEdge("flows", v11, id, 25);
        v7.addEdge("flows", v12, id, 26);
        v7.addEdge("flows", v13, id, 27);

        g.V().hasLabel("ABC").has("alive", "yes").
                sack(assign).by("Val").
                repeat(out("flows").has("alive", "yes").simplePath().sack(ClarisseOperator.sub).by("Val").property("Val", sack())).
                until(hasLabel("XZ").has("alive", "yes")).iterate();

        g.V().valueMap().map(t -> {
            // make array output readable
            final Map<String, Object> vm = t.get();
            vm.computeIfPresent("Val", (k, v) -> Arrays.toString(((List<double[]>) v).get(0)));
            return vm;
        }).forEachRemaining(System.out::println);
    }

    public enum ClarisseOperator implements BinaryOperator<Object> {

        sub {
            public Object apply(final Object a, final Object b) {

                int k;
                final double[] curr = (double[]) a;
                final double[] prev = (double[]) b;
                final double[] result = new double[k = curr.length * prev.length / 2];

                for (int j = curr.length; j > 0; j -= 2) {
                    for (int i = prev.length; i > 0; j += 2) {
                        result[--k] = curr[--j] - prev[--i];
                        result[--k] = curr[--j] - prev[--i];
                    }
                }

                return result;
            }
        }
    }
}

output

{Val=[10.0, 15.0], alive=[yes]}
{Val=[9.0, 12.0, 4.0, 6.0], alive=[yes]}
{Val=[4.0, 10.0, -1.0, 4.0], alive=[yes]}
{Val=[1.0, 7.0], alive=[no]}
{Val=[3.0, 2.0, -2.0, -4.0], alive=[yes]}
{Val=[1.0, 6.0, -4.0, 0.0], alive=[yes]}
{Val=[1.0, 5.0], alive=[yes]}
{Val=[1.0, 9.0], alive=[yes]}