Examples with Arborescence ai.grakn.graql.internal.gremlin.spanningtree.Arborescence used on opensource projects

Example 1 with Arborescence

use of ai.grakn.graql.internal.gremlin.spanningtree.Arborescence in project grakn by graknlabs.

the class GreedyTraversalPlan method greedyTraversal.

private static void greedyTraversal(List<Fragment> plan, Arborescence<Node> arborescence, Map<NodeId, Node> nodes, Map<Node, Map<Node, Fragment>> edgeFragmentChildToParent) {
    Map<Node, Set<Node>> edgesParentToChild = new HashMap<>();
    arborescence.getParents().forEach((child, parent) -> {
        if (!edgesParentToChild.containsKey(parent)) {
            edgesParentToChild.put(parent, new HashSet<>());
        }
        edgesParentToChild.get(parent).add(child);
    });
    Node root = arborescence.getRoot();
    Set<Node> reachableNodes = Sets.newHashSet(root);
    while (!reachableNodes.isEmpty()) {
        Optional<Node> optionalNodeWithMinCost = reachableNodes.stream().min(Comparator.comparingDouble(node -> branchWeight(node, arborescence, edgesParentToChild, edgeFragmentChildToParent)));
        assert optionalNodeWithMinCost.isPresent() : "reachableNodes is never empty, so there is always a minimum";
        Node nodeWithMinCost = optionalNodeWithMinCost.get();
        // add edge fragment first, then node fragments
        getEdgeFragment(nodeWithMinCost, arborescence, edgeFragmentChildToParent).ifPresent(plan::add);
        addNodeFragmentToPlan(nodeWithMinCost, plan, nodes, true);
        reachableNodes.remove(nodeWithMinCost);
        if (edgesParentToChild.containsKey(nodeWithMinCost)) {
            reachableNodes.addAll(edgesParentToChild.get(nodeWithMinCost));
        }
    }
}