Examples with TarjansSCCAlgorithm com.graphhopper.routing.subnetwork.TarjansSCCAlgorithm used on opensource projects

Example 1 with TarjansSCCAlgorithm

use of com.graphhopper.routing.subnetwork.TarjansSCCAlgorithm in project graphhopper by graphhopper.

the class LandmarkStorage method createLandmarks.

/**
     * This method calculates the landmarks and initial weightings to & from them.
     */
public void createLandmarks() {
    if (isInitialized())
        throw new IllegalStateException("Initialize the landmark storage only once!");
    // fill 'from' and 'to' weights with maximum value
    long maxBytes = (long) graph.getNodes() * LM_ROW_LENGTH;
    this.landmarkWeightDA.create(2000);
    this.landmarkWeightDA.ensureCapacity(maxBytes);
    for (long pointer = 0; pointer < maxBytes; pointer += 2) {
        landmarkWeightDA.setShort(pointer, (short) SHORT_INFINITY);
    }
    String additionalInfo = "";
    // guess the factor
    if (factor <= 0) {
        // A 'factor' is necessary to store the weight in just a short value but without loosing too much precision.
        // This factor is rather delicate to pick, we estimate it through the graph boundaries its maximum distance.
        // For small areas we use max_bounds_dist*X and otherwise we use a big fixed value for this distance.
        // If we would pick the distance too big for small areas this could lead to (slightly) suboptimal routes as there
        // will be too big rounding errors. But picking it too small is dangerous regarding performance
        // e.g. for Germany at least 1500km is very important otherwise speed is at least twice as slow e.g. for just 1000km
        BBox bounds = graph.getBounds();
        double distanceInMeter = Helper.DIST_EARTH.calcDist(bounds.maxLat, bounds.maxLon, bounds.minLat, bounds.minLon) * 7;
        if (distanceInMeter > 50_000 * 7 || /* for tests and convenience we do for now: */
        !bounds.isValid())
            distanceInMeter = 30_000_000;
        double maxWeight = weighting.getMinWeight(distanceInMeter);
        setMaximumWeight(maxWeight);
        additionalInfo = ", maxWeight:" + maxWeight + ", from max distance:" + distanceInMeter / 1000f + "km";
    }
    LOGGER.info("init landmarks for subnetworks with node count greater than " + minimumNodes + " with factor:" + factor + additionalInfo);
    // special subnetwork 0
    int[] empty = new int[landmarks];
    Arrays.fill(empty, UNSET_SUBNETWORK);
    landmarkIDs.add(empty);
    byte[] subnetworks = new byte[graph.getNodes()];
    Arrays.fill(subnetworks, (byte) UNSET_SUBNETWORK);
    EdgeFilter tarjanFilter = new DefaultEdgeFilter(encoder, false, true);
    IntHashSet blockedEdges = new IntHashSet();
    // the ruleLookup splits certain areas from each other but avoids making this a permanent change so that other algorithms still can route through these regions.
    if (ruleLookup != null && ruleLookup.size() > 0) {
        StopWatch sw = new StopWatch().start();
        blockedEdges = findBorderEdgeIds(ruleLookup);
        tarjanFilter = new BlockedEdgesFilter(encoder, false, true, blockedEdges);
        LOGGER.info("Made " + blockedEdges.size() + " edges inaccessible. Calculated country cut in " + sw.stop().getSeconds() + "s, " + Helper.getMemInfo());
    }
    StopWatch sw = new StopWatch().start();
    // we cannot reuse the components calculated in PrepareRoutingSubnetworks as the edgeIds changed in between (called graph.optimize)
    // also calculating subnetworks from scratch makes bigger problems when working with many oneways
    TarjansSCCAlgorithm tarjanAlgo = new TarjansSCCAlgorithm(graph, tarjanFilter, true);
    List<IntArrayList> graphComponents = tarjanAlgo.findComponents();
    LOGGER.info("Calculated tarjan subnetworks in " + sw.stop().getSeconds() + "s, " + Helper.getMemInfo());
    EdgeExplorer tmpExplorer = graph.createEdgeExplorer(new RequireBothDirectionsEdgeFilter(encoder));
    int nodes = 0;
    for (IntArrayList subnetworkIds : graphComponents) {
        nodes += subnetworkIds.size();
        if (subnetworkIds.size() < minimumNodes)
            continue;
        int index = subnetworkIds.size() - 1;
        // ensure start node is reachable from both sides and no subnetwork is associated
        for (; index >= 0; index--) {
            int nextStartNode = subnetworkIds.get(index);
            if (subnetworks[nextStartNode] == UNSET_SUBNETWORK && GHUtility.count(tmpExplorer.setBaseNode(nextStartNode)) > 0) {
                GHPoint p = createPoint(graph, nextStartNode);
                LOGGER.info("start node: " + nextStartNode + " (" + p + ") subnetwork size: " + subnetworkIds.size() + ", " + Helper.getMemInfo() + ((ruleLookup == null) ? "" : " area:" + ruleLookup.lookupRule(p).getId()));
                if (createLandmarksForSubnetwork(nextStartNode, subnetworks, blockedEdges))
                    break;
            }
        }
        if (index < 0)
            LOGGER.warn("next start node not found in big enough network of size " + subnetworkIds.size() + ", first element is " + subnetworkIds.get(0) + ", " + createPoint(graph, subnetworkIds.get(0)));
    }
    int subnetworkCount = landmarkIDs.size();
    // store all landmark node IDs and one int for the factor itself.
    this.landmarkWeightDA.ensureCapacity(maxBytes + /* landmark weights */
    subnetworkCount * landmarks);
    // calculate offset to point into landmark mapping
    long bytePos = maxBytes;
    for (int[] landmarks : landmarkIDs) {
        for (int lmNodeId : landmarks) {
            landmarkWeightDA.setInt(bytePos, lmNodeId);
            bytePos += 4L;
        }
    }
    landmarkWeightDA.setHeader(0 * 4, graph.getNodes());
    landmarkWeightDA.setHeader(1 * 4, landmarks);
    landmarkWeightDA.setHeader(2 * 4, subnetworkCount);
    if (factor * DOUBLE_MLTPL > Integer.MAX_VALUE)
        throw new UnsupportedOperationException("landmark weight factor cannot be bigger than Integer.MAX_VALUE " + factor * DOUBLE_MLTPL);
    landmarkWeightDA.setHeader(3 * 4, (int) Math.round(factor * DOUBLE_MLTPL));
    // serialize fast byte[] into DataAccess
    subnetworkStorage.create(graph.getNodes());
    for (int nodeId = 0; nodeId < subnetworks.length; nodeId++) {
        subnetworkStorage.setSubnetwork(nodeId, subnetworks[nodeId]);
    }
    LOGGER.info("Finished landmark creation. Subnetwork node count sum " + nodes + " vs. nodes " + graph.getNodes());
    initialized = true;
}