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bidirectional_dijkstra_test.cc
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bidirectional_dijkstra_test.cc
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// Copyright 2010-2024 Google LLC
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#include "ortools/graph/bidirectional_dijkstra.h"
#include <cmath>
#include <limits>
#include <random>
#include <string>
#include <utility>
#include <vector>
#include "absl/base/log_severity.h"
#include "absl/container/flat_hash_map.h"
#include "absl/random/distributions.h"
#include "absl/strings/str_cat.h"
#include "absl/types/span.h"
#include "gtest/gtest.h"
#include "ortools/base/gmock.h"
#include "ortools/base/iterator_adaptors.h"
#include "ortools/graph/bounded_dijkstra.h"
#include "ortools/graph/graph.h"
namespace operations_research {
namespace {
using ::testing::AnyOf;
using ::testing::ElementsAre;
using ::testing::ElementsAreArray;
using ::testing::IsEmpty;
using ::util::ListGraph;
using ::util::StaticGraph;
TEST(BidirectionalDijkstraTest, EmptyPathInspection) {
ListGraph<> empty_graph;
std::vector<double> empty_vector;
BidirectionalDijkstra<ListGraph<>, double> dijkstra(
&empty_graph, &empty_vector, &empty_graph, &empty_vector);
const auto path = dijkstra.SetToSetShortestPath({}, {});
ASSERT_EQ(path.meeting_point, -1);
EXPECT_THAT(dijkstra.PathToNodePath(path), IsEmpty());
EXPECT_EQ(dijkstra.PathDebugString(path), "<NO PATH>");
}
TEST(BidirectionalDijkstraTest, SmallTest) {
// Build a small "grid" graph. Arc indices and lengths of the forward graph
// are in (); and the backward graph has the same, but reversed arcs.
//
// 0 --(#0:0.1)--> 1 --(#1:1.1)--> 2
// | | |
// (#2:0.1) (#3:0.19) (#4:0.3)
// | | |
// v v v
// 3 --(#5:0.2)--> 4 --(#6:1.2)--> 5
ListGraph<> forward_graph;
std::vector<double> arc_lengths;
forward_graph.AddArc(0, 1);
arc_lengths.push_back(0.1);
forward_graph.AddArc(1, 2);
arc_lengths.push_back(1.1);
forward_graph.AddArc(0, 3);
arc_lengths.push_back(0.1);
forward_graph.AddArc(1, 4);
arc_lengths.push_back(0.19);
forward_graph.AddArc(2, 5);
arc_lengths.push_back(0.3);
forward_graph.AddArc(3, 4);
arc_lengths.push_back(0.2);
forward_graph.AddArc(4, 5);
arc_lengths.push_back(1.2);
ListGraph<> backward_graph;
for (int arc = 0; arc < forward_graph.num_arcs(); ++arc) {
backward_graph.AddArc(forward_graph.Head(arc), forward_graph.Tail(arc));
}
BidirectionalDijkstra<ListGraph<>, double> dijkstra(
&forward_graph, &arc_lengths, &backward_graph, &arc_lengths);
// Since the meeting point may vary, depending on which search direction goes
// faster, we run it many times to try and exercise more code paths.
const int kNumPaths = 1000;
for (int i = 0; i < kNumPaths; ++i) {
SCOPED_TRACE(absl::StrCat("On attempt #", i));
const auto path = dijkstra.OneToOneShortestPath(0, 5);
EXPECT_THAT(dijkstra.PathToNodePath(path), ElementsAre(0, 1, 4, 5));
ASSERT_THAT(dijkstra.PathDebugString(path),
AnyOf("0 --(#0:0.1)--> 1 --(#3:0.19)--> 4 --(#6:1.2)--> [5]",
"0 --(#0:0.1)--> 1 --(#3:0.19)--> [4] <--(#6:1.2)-- 5",
"0 --(#0:0.1)--> [1] <--(#3:0.19)-- 4 <--(#6:1.2)-- 5",
"[0] <--(#0:0.1)-- 1 <--(#3:0.19)-- 4 <--(#6:1.2)-- 5"));
}
}
TEST(BidirectionalDijkstraTest, RandomizedCorrectnessTest) {
std::mt19937 random(12345);
const int kNumGraphs = DEBUG_MODE ? 100 : 300;
const int kNumQueriesPerGraph = DEBUG_MODE ? 10 : 30;
const int kNumNodes = 1000;
const int kNumArcs = 10000;
for (int graph_iter = 0; graph_iter < kNumGraphs; ++graph_iter) {
// Build the random graphs.
StaticGraph<> forward_graph;
StaticGraph<> backward_graph;
std::vector<double> forward_lengths;
std::vector<double> backward_lengths;
std::vector<int> forward_arc_of_backward_arc;
forward_graph.AddNode(kNumNodes - 1);
backward_graph.AddNode(kNumNodes - 1);
for (int i = 0; i < kNumArcs; ++i) {
const int a = absl::Uniform(random, 0, kNumNodes);
const int b = absl::Uniform(random, 0, kNumNodes);
forward_graph.AddArc(a, b);
backward_graph.AddArc(b, a);
forward_arc_of_backward_arc.push_back(i);
const double length = absl::Uniform<double>(random, 0.0, 1.0);
forward_lengths.push_back(length);
backward_lengths.push_back(length);
}
std::vector<int> forward_perm;
forward_graph.Build(&forward_perm);
util::Permute(forward_perm, &forward_lengths);
for (int& a : forward_arc_of_backward_arc) {
a = forward_perm[a];
}
std::vector<int> backward_perm;
backward_graph.Build(&backward_perm);
util::Permute(backward_perm, &backward_lengths);
util::Permute(backward_perm, &forward_arc_of_backward_arc);
// Initialize the tested Dijkstra and the reference Dijkstra.
typedef BidirectionalDijkstra<StaticGraph<>, double> Dijkstra;
Dijkstra tested_dijkstra(&forward_graph, &forward_lengths, &backward_graph,
&backward_lengths);
BoundedDijkstraWrapper<StaticGraph<>, double> ref_dijkstra(
&forward_graph, &forward_lengths);
// To print some debugging info in case the test fails.
auto print_arc_path = [&](absl::Span<const int> arc_path) -> std::string {
if (arc_path.empty()) return "<EMPTY>";
std::string out = absl::StrCat(forward_graph.Tail(arc_path[0]));
double total_length = 0.0;
for (const int arc : arc_path) {
absl::StrAppend(&out, "--(#", arc, ":", (forward_lengths[arc]), ")-->",
forward_graph.Head(arc));
total_length += forward_lengths[arc];
}
absl::StrAppend(&out, "; Total length=", (total_length));
return out;
};
auto print_node_distances =
[&](absl::Span<const Dijkstra::NodeDistance> nds) -> std::string {
std::string out = "{";
for (const Dijkstra::NodeDistance& nd : nds) {
absl::StrAppend(&out, " #", nd.node, " dist=", (nd.distance), ",");
}
if (!nds.empty()) out.back() = ' '; // Replace the last ','.
out += '}';
return out;
};
// Run random Dijkstra queries.
for (int q = 0; q < kNumQueriesPerGraph; ++q) {
const int num_src = ceil(absl::Exponential<double>(random));
const int num_dst = ceil(absl::Exponential<double>(random));
std::vector<std::pair<int, double>> ref_srcs;
std::vector<std::pair<int, double>> ref_dsts;
std::vector<Dijkstra::NodeDistance> srcs;
std::vector<Dijkstra::NodeDistance> dsts;
for (int i = 0; i < num_src; ++i) {
const int src = absl::Uniform(random, 0, kNumNodes);
// Try costs < 0.
const double dist = absl::Uniform<double>(random, 1.0, 2.0);
ref_srcs.push_back({src, dist});
srcs.push_back({src, dist});
}
for (int i = 0; i < num_dst; ++i) {
const int dst = absl::Uniform(random, 0, kNumNodes);
const double dist = absl::Uniform<double>(random, 1.0, 2.0);
ref_dsts.push_back({dst, dist});
dsts.push_back({dst, dist});
}
const std::vector<int> ref_dests =
ref_dijkstra
.RunBoundedDijkstraFromMultipleSourcesToMultipleDestinations(
ref_srcs, ref_dsts,
/*num_destinations_to_reach=*/1,
std::numeric_limits<double>::infinity());
if (ref_dests.empty()) {
// No path. Verify that.
EXPECT_EQ(
tested_dijkstra.SetToSetShortestPath(srcs, dsts).meeting_point, -1);
continue;
}
const std::vector<int> ref_arc_path =
ref_dijkstra.ArcPathToNode(ref_dests[0]);
const auto path = tested_dijkstra.SetToSetShortestPath(srcs, dsts);
std::vector<int> arc_path = path.forward_arc_path;
for (const int arc : ::gtl::reversed_view(path.backward_arc_path)) {
arc_path.push_back(forward_arc_of_backward_arc[arc]);
}
ASSERT_THAT(arc_path, ElementsAreArray(ref_arc_path))
<< "On graph #" << graph_iter << ", query #" << q
<< "\nSources : " << print_node_distances(srcs)
<< "\nDestinations: " << print_node_distances(dsts)
<< "\nReference path : " << print_arc_path(ref_arc_path)
<< "\nObtained path : " << print_arc_path(arc_path);
}
}
}
} // namespace
} // namespace operations_research