C++ WorkQueue::capacity方法代码示例

// generalized equivalence processing (left and right)
// basically, goes through every vertex in a class and checks if all successor or
// predecessor classes match in all vertices. if classes mismatch, a vertex is
// split into a separate class, along with all vertices having the same set of
// successor/predecessor classes. the opposite side (successors for left
// equivalence, predecessors for right equivalence) classes get revalidated in
// case of a split.
static
void equivalence(vector<VertexInfoSet> &classes, WorkQueue &work_queue,
                 EquivalenceType eq_type) {
    // now, go through the work queue until it's empty
    map<flat_set<unsigned>, VertexInfoSet> tentative_classmap;
    flat_set<unsigned> cur_classes;
    // local work queue, to store classes we want to revalidate in case of split
    WorkQueue reval_queue(work_queue.capacity());

    while (!work_queue.empty()) {
        // dequeue our class from the work queue
        unsigned cur_class = work_queue.pop();

        // get all vertices in current equivalence class
        VertexInfoSet &cur_class_vertices = classes.at(cur_class);

        if (cur_class_vertices.size() < 2) {
            continue;
        }

        // clear data from previous iterations
        tentative_classmap.clear();

        DEBUG_PRINTF("doing equivalence pass for class %u, %zd vertices\n",
                     cur_class, cur_class_vertices.size());

        // go through vertices in this class
        for (VertexInfo *vi : cur_class_vertices) {
            cur_classes.clear();

            // get vertex lists for equivalence vertices and vertices for
            // revalidation in case of split
            const auto &eq_vertices =
                (eq_type == LEFT_EQUIVALENCE) ? vi->pred : vi->succ;
            const auto &reval_vertices =
                (eq_type == LEFT_EQUIVALENCE) ? vi->succ : vi->pred;

            // go through equivalence and note the classes
            for (const VertexInfo *tmp : eq_vertices) {
                cur_classes.insert(tmp->equivalence_class);
            }

            // note all the classes that need to be reevaluated
            for (const VertexInfo *tmp : reval_vertices) {
                reval_queue.push(tmp->equivalence_class);
            }

            VertexInfoSet &tentative_classes = tentative_classmap[cur_classes];
            tentative_classes.insert(vi);
        }

        // if we found more than one class, split and revalidate everything
        if (tentative_classmap.size() > 1) {
            auto tmi = tentative_classmap.begin();

            // start from the second class
            for (++tmi; tmi != tentative_classmap.end(); ++tmi) {
                const VertexInfoSet &vertices_to_split = tmi->second;
                unsigned new_class = classes.size();
                VertexInfoSet new_class_vertices;

                for (VertexInfo *vi : vertices_to_split) {
                    vi->equivalence_class = new_class;
                    // note: we cannot use the cur_class_vertices ref, as it is
                    // invalidated by modifications to the classes vector.
                    classes[cur_class].erase(vi);
                    new_class_vertices.insert(vi);
                }
                classes.push_back(move(new_class_vertices));

                if (contains(tmi->first, cur_class)) {
                    reval_queue.push(new_class);
                }
            }
            work_queue.append(reval_queue);
        }
        reval_queue.clear();
    }
}