implement batch delete for paths

bdsg/include/bdsg/hash_graph.hpp

@@ -269,6 +269,11 @@ class HashGraph : public MutablePathDeletableHandleGraph, public SerializableHan
      */
     void destroy_path(const path_handle_t& path);
 
+    /**
+    * Destroy the given set of paths. Invalidates handles to all the paths and their steps.
+    */
+    void destroy_paths(const std::vector<path_handle_t>& paths);
+
     /**
      * Create a path with the given name. The caller must ensure that no path
      * with the given name exists already, or the behavior is undefined.

bdsg/include/bdsg/internal/base_packed_graph.hpp

@@ -333,6 +333,11 @@ class BasePackedGraph {
      * Destroy the given path. Invalidates handles to the path and its node steps.
      */
     void destroy_path(const path_handle_t& path);
+
+    /**
+     * Destroy the given set of paths. Invalidates handles to all the paths and their steps.
+     */
+    void destroy_paths(const std::vector<path_handle_t>& paths);
 
     /**
      * Create a path with the given name. The caller must ensure that no path
@@ -2607,52 +2612,76 @@ string BasePackedGraph<Backend>::decode_path_name(const int64_t& path_idx) const
 
 template<typename Backend>
 void BasePackedGraph<Backend>::destroy_path(const path_handle_t& path) {
+    destroy_paths({path});
+}
+
+template<typename Backend>
+void BasePackedGraph<Backend>::destroy_paths(const std::vector<path_handle_t>& paths) {
 
-    PackedPath& packed_path = paths.at(as_integer(path));
+    std::unordered_set<path_handle_t> paths_set(paths.begin(), paths.end());
 
-    // remove node membership records corresponding to this path
-    bool first_iter = true;
-    for (uint64_t step_offset = path_head_iv.get(as_integer(path));
-         step_offset != 0 && (step_offset != path_head_iv.get(as_integer(path)) || first_iter);
-         step_offset = get_step_next(packed_path, step_offset)) {
-
-        uint64_t trav = get_step_trav(packed_path, step_offset);
-        size_t node_member_idx = graph_index_to_node_member_index(graph_iv_index(decode_traversal(trav)));
+    PackedSet<Backend> nodes_visited;
+
+    for (const auto& path : paths) {
 
-        // find a membership record for this path
-        size_t prev = 0;
-        size_t here = path_membership_node_iv.get(node_member_idx);
-        while (as_path_handle(get_membership_path(here)) != path) {
-            prev = here;
-            here = get_next_membership(here);
-            // note: we don't need to be careful about getting the exact corresponding step since this node
-            // should try to delete a membership record exactly as many times as it occurs on this path -- all of
-            // the records will get deleted
-        }
+        PackedPath& packed_path = this->paths.at(as_integer(path));
 
-        if (prev == 0) {
-            // this was the first record, set following one to be the head
-            path_membership_node_iv.set(node_member_idx, get_next_membership(here));
-        }
-        else {
-            // make the link from the previous record skip over the current one
-            set_next_membership(prev, get_next_membership(here));
+        // remove node membership records corresponding to this path
+        bool first_iter = true;
+        for (uint64_t step_offset = path_head_iv.get(as_integer(path));
+             step_offset != 0 && (step_offset != path_head_iv.get(as_integer(path)) || first_iter);
+             step_offset = get_step_next(packed_path, step_offset)) {
+
+            uint64_t trav = get_step_trav(packed_path, step_offset);
+            // if there are multiple paths, we check for whether we've gone over the same
+            // node multiple times (which would be wasteful)
+            if (paths.size() > 1) {
+                nid_t node_id = get_id(decode_traversal(trav));
+                if (nodes_visited.find(node_id)) {
+                    continue;
+                }
+                nodes_visited.insert(node_id);
+            }
+
+            size_t node_member_idx = graph_index_to_node_member_index(graph_iv_index(decode_traversal(trav)));
+
+            // find a membership record for this path
+            size_t prev = 0;
+            size_t here = path_membership_node_iv.get(node_member_idx);
+            while (here) {
+                if (paths_set.count(as_path_handle(get_membership_path(here)))) {
+                    // this is a membership record for a path that we're deleting
+                    if (prev == 0) {
+                        // this was the first record, set following one to be the head
+                        path_membership_node_iv.set(node_member_idx, get_next_membership(here));
+                    }
+                    else {
+                        // make the link from the previous record skip over the current one
+                        set_next_membership(prev, get_next_membership(here));
+                    }
+
+                    ++deleted_membership_records;
+                }
+                else {
+                    prev = here;
+                }
+
+                here = get_next_membership(here);
+            }
+
+            first_iter = false;
         }
 
-        ++deleted_membership_records;
+        path_id.erase(extract_encoded_path_name(as_integer(path)));
 
-        first_iter = false;
+        path_is_deleted_iv.set(as_integer(path), true);
+        packed_path.steps_iv.clear();
+        packed_path.links_iv.clear();
+        path_head_iv.set(as_integer(path), 0);
+        path_tail_iv.set(as_integer(path), 0);
+        path_deleted_steps_iv.set(as_integer(path), 0);
     }
 
-    path_id.erase(extract_encoded_path_name(as_integer(path)));
-
-    path_is_deleted_iv.set(as_integer(path), true);
-    packed_path.steps_iv.clear();
-    packed_path.links_iv.clear();
-    path_head_iv.set(as_integer(path), 0);
-    path_tail_iv.set(as_integer(path), 0);
-    path_deleted_steps_iv.set(as_integer(path), 0);
-
     defragment();
 }
 

bdsg/include/bdsg/internal/packed_structs.hpp

@@ -1370,9 +1370,6 @@ inline uint64_t PackedSet<Backend>::optimal_anchor() const {
 
 template<typename Backend>
 inline void PackedSet<Backend>::rehash(bool shrink) {
-    // Keeping the RNG state in the class isn't bvery portable, so we make one
-    // per thread in thread storage.
-    static thread_local default_random_engine gen(random_device{}());
 
     // move to the next size in the schedule
     if (shrink) {
@@ -1390,6 +1387,10 @@ inline void PackedSet<Backend>::rehash(bool shrink) {
     PackedVec new_table;
     new_table.resize(bdsg_packed_set_size_schedule[schedule_val]);
 
+    // we use random-at-coding-time linear congruential generator to get a pseudo-random seed
+    // that makes the coefficients in a deterministic, system-independent way
+    uint64_t seed = 17340519333326003581ull * (schedule_val + 14057138822558802453ull) + 6918838906415272680ull;
+    std::mt19937_64 gen(seed);
     std::uniform_int_distribution<uint64_t> distr(0, new_table.size() - 1);
     for (size_t i = 0; i < 5; ++i) {
         coefs[i] = distr(gen);
@@ -1511,9 +1512,6 @@ inline void PackedSet<Backend>::set_load_factors(double min_load_factor, double
     assert(max_load_factor < 1.0);
     min_load = min_load_factor;
     max_load = max_load_factor;
-    assert(max_load > min_load);
-    assert(min_load >= 0.0);
-    assert(max_load < 1.0);
     if (table.size() > 0) {
         while (num_items <= min_load * table.size()) {
             rehash(true);

bdsg/src/hash_graph.cpp

@@ -592,25 +592,46 @@ namespace bdsg {
         }
         return true;
     }
-    
+
     void HashGraph::destroy_path(const path_handle_t& path) {
+        destroy_paths({path});
+    }
+
+    void HashGraph::destroy_paths(const vector<path_handle_t>& paths) {
 
-        // remove the records of nodes occurring on this path
-        for_each_step_in_path(path, [&](const step_handle_t& step) {
-            path_mapping_t* mapping = (path_mapping_t*) intptr_t(as_integers(step)[1]);
-            vector<path_mapping_t*>& node_occs = graph[get_id(mapping->handle)].occurrences;
-            for (size_t i = 0; i < node_occs.size(); i++) {
-                if (node_occs[i] == mapping) {
-                    node_occs[i] = node_occs.back();
-                    node_occs.pop_back();
-                    break;
-                }
-            }
-        });
+        unordered_set<int64_t> path_ids;
+        for (auto path : paths) {
+            path_ids.emplace(as_integer(path));
+        }
+        unordered_set<nid_t> nodes_visited;
 
-        // erase the path itself
-        path_id.erase(paths[as_integer(path)].name);
-        paths.erase(as_integer(path));
+        for (auto path : paths) {
+            // remove the records of nodes occurring on this path
+            for_each_step_in_path(path, [&](const step_handle_t& step) {
+                path_mapping_t* mapping = (path_mapping_t*) intptr_t(as_integers(step)[1]);
+                if (paths.size() > 1) {
+                    bool did_insert = nodes_visited.insert(get_id(mapping->handle)).second;
+                    if (!did_insert) {
+                        // we've already deleted on this node
+                        return;
+                    }
+                }
+                vector<path_mapping_t*>& node_occs = graph[get_id(mapping->handle)].occurrences;
+                for (size_t i = 0; i < node_occs.size(); ) {
+                    if (path_ids.count(node_occs[i]->path_id)) {
+                        node_occs[i] = node_occs.back();
+                        node_occs.pop_back();
+                    }
+                    else {
+                        ++i;
+                    }
+                }
+            });
+
+            // erase the path itself
+            path_id.erase(this->paths[as_integer(path)].name);
+            this->paths.erase(as_integer(path));
+        }
     }
 
     path_handle_t HashGraph::create_path_handle(const string& name, bool is_circular) {

bdsg/src/test_libbdsg.cpp

@@ -2285,6 +2285,73 @@ void test_deletable_handle_graphs() {
         }
     }
 
+    // batch deletion of paths works as expected
+    {
+        vector<MutablePathDeletableHandleGraph*> implementations;
+
+        // Add implementations
+
+        PackedGraph pg;
+        implementations.push_back(&pg);
+
+        HashGraph hg;
+        implementations.push_back(&hg);
+
+        MappedPackedGraph mpg;
+        implementations.push_back(&mpg);
+
+        for (int imp = 0; imp < implementations.size(); ++imp) {
+
+            MutablePathDeletableHandleGraph& graph = *implementations[imp];
+
+            auto h1 = graph.create_handle("A");
+            auto h2 = graph.create_handle("A");
+            auto h3 = graph.create_handle("A");
+
+            graph.create_edge(h1, h2);
+            graph.create_edge(h2, h3);
+
+            auto p1 = graph.create_path_handle("1");
+            auto p2 = graph.create_path_handle("2");
+            auto p3 = graph.create_path_handle("3");
+            auto p4 = graph.create_path_handle("4");
+            auto p5 = graph.create_path_handle("5");
+
+            for (const auto& p : {p1, p2, p3, p4, p5}) {
+                for (auto h : {h1, h2, h3}) {
+                    graph.append_step(p, h);
+                }
+            }
+
+            graph.destroy_paths({p1, p3, p4});
+
+            set<path_handle_t> paths_seen;
+            set<path_handle_t> paths_expected{p2, p5};
+            graph.for_each_path_handle([&](const path_handle_t& path) {
+                assert(!paths_seen.count(path));
+                paths_seen.insert(path);
+                std::vector<handle_t> handles;
+                std::vector<handle_t> handles_expected{h1, h2, h3};
+                for (auto h : graph.scan_path(path)) {
+                    handles.push_back(h);
+                }
+                assert(handles == handles_expected);
+            });
+
+            assert(paths_seen == paths_expected);
+
+            graph.for_each_handle([&](const handle_t& h) {
+                set<path_handle_t> paths;
+                graph.for_each_step_on_handle(h, [&](const step_handle_t& step) {
+                    auto p = graph.get_path_handle_of_step(step);
+                    assert(!paths.count(p));
+                    paths.insert(p);
+                });
+                assert(paths_seen == paths_expected);
+            });
+        }
+    }
+
     cerr << "DeletableHandleGraph tests successful!" << endl;
 }