tpl_net_test.cc

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/*
                          Aleph_w
 
  Data structures & Algorithms
  version 2.0.0b
  https://github.com/lrleon/Aleph-w
 
  This file is part of Aleph-w library
 
  Copyright (c) 2002-2026 Leandro Rabindranath Leon
 
  Permission is hereby granted, free of charge, to any person obtaining a copy
  of this software and associated documentation files (the "Software"), to deal
  in the Software without restriction, including without limitation the rights
  to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
  copies of the Software, and to permit persons to whom the Software is
  furnished to do so, subject to the following conditions:
 
  The above copyright notice and this permission notice shall be included in all
  copies or substantial portions of the Software.
 
  THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
  IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
  FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
  AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
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  OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
  SOFTWARE.
*/
 
 
 
#include <gtest/gtest.h>
 
#include <set>
 
#include <tpl_net.H>
 
using namespace Aleph;
 
namespace
{
  using Net = Net_Graph<Net_Node<int>, Net_Arc<int, int>>;
 
  struct SimpleNet
  {
    Net::Node *s = nullptr;
    Net::Node *a = nullptr;
    Net::Node *b = nullptr;
    Net::Node *t = nullptr;
    Net::Arc *sa = nullptr;
    Net::Arc *sb = nullptr;
    Net::Arc *ab = nullptr;
    Net::Arc *at = nullptr;
    Net::Arc *bt = nullptr;
  };
 
  SimpleNet build_simple_net(Net &net)
  {
    SimpleNet sn;
    sn.s = net.insert_node(0);
    sn.a = net.insert_node(1);
    sn.b = net.insert_node(2);
    sn.t = net.insert_node(3);
 
    sn.sa = net.insert_arc(sn.s, sn.a, 3, 0);
    sn.sb = net.insert_arc(sn.s, sn.b, 2, 0);
    sn.ab = net.insert_arc(sn.a, sn.b, 1, 0);
    sn.at = net.insert_arc(sn.a, sn.t, 2, 0);
    sn.bt = net.insert_arc(sn.b, sn.t, 3, 0);
 
    return sn;
  }
 
  struct SingleArcNet
  {
    Net::Node *s = nullptr;
    Net::Node *t = nullptr;
    Net::Arc *st = nullptr;
  };
 
  SingleArcNet build_single_arc(Net &net, int cap, int flow = 0)
  {
    SingleArcNet sn;
    sn.s = net.insert_node(0);
    sn.t = net.insert_node(1);
    sn.st = net.insert_arc(sn.s, sn.t, cap, flow);
    return sn;
  }
}
 
TEST(NetGraphBasics, SourcesSinksUpdateOnArcOperations)
{
  Net net;
  auto s = net.insert_node(1);
  auto t = net.insert_node(2);
 
  EXPECT_TRUE(net.is_source(s));
  EXPECT_TRUE(net.is_sink(s));
  EXPECT_TRUE(net.is_source(t));
  EXPECT_TRUE(net.is_sink(t));
 
  auto arc = net.insert_arc(s, t, 5, 0);
 
  EXPECT_TRUE(net.is_source(s));
  EXPECT_FALSE(net.is_sink(s));
  EXPECT_FALSE(net.is_source(t));
  EXPECT_TRUE(net.is_sink(t));
 
  net.remove_arc(arc);
 
  EXPECT_TRUE(net.is_source(s));
  EXPECT_TRUE(net.is_sink(s));
  EXPECT_TRUE(net.is_source(t));
  EXPECT_TRUE(net.is_sink(t));
}
 
TEST(NetGraphBasics, DisconnectConnectArcUpdatesSets)
{
  Net net;
  auto s = net.insert_node(1);
  auto t = net.insert_node(2);
  auto arc = net.insert_arc(s, t, 5, 0);
 
  net.disconnect_arc(arc);
  EXPECT_EQ(net.get_num_arcs(), 0U);
  EXPECT_TRUE(net.is_source(t));
  EXPECT_TRUE(net.is_sink(s));
 
  net.connect_arc(arc);
  EXPECT_EQ(net.get_num_arcs(), 1U);
  EXPECT_FALSE(net.is_source(t));
  EXPECT_FALSE(net.is_sink(s));
}
 
TEST(NetGraphSuperNodes, MakeAndUnmakeSuperSource)
{
  Net net;
  auto s1 = net.insert_node(1);
  auto s2 = net.insert_node(2);
  auto t1 = net.insert_node(3);
  auto t2 = net.insert_node(4);
 
  net.insert_arc(s1, t1, 5, 0);
  net.insert_arc(s2, t2, 7, 0);
 
  EXPECT_EQ(net.get_src_nodes().size(), 2U);
  EXPECT_EQ(net.get_sink_nodes().size(), 2U);
 
  const auto before_nodes = net.get_num_nodes();
  net.make_super_source();
 
  EXPECT_EQ(net.get_src_nodes().size(), 1U);
  EXPECT_EQ(net.get_num_nodes(), before_nodes + 1);
 
  auto super_source = net.get_source();
  EXPECT_EQ(net.get_out_degree(super_source), 2U);
 
  bool has_self = false;
  for (Node_Arc_Iterator<Net> it(super_source); it.has_curr(); it.next_ne())
    {
      if (it.get_tgt_node_ne() == super_source)
        has_self = true;
    }
  EXPECT_FALSE(has_self);
 
  net.unmake_super_source();
  EXPECT_EQ(net.get_num_nodes(), before_nodes);
  EXPECT_EQ(net.get_src_nodes().size(), 2U);
}
 
TEST(NetGraphSuperNodes, MakeAndUnmakeSuperSink)
{
  Net net;
  auto s1 = net.insert_node(1);
  auto s2 = net.insert_node(2);
  auto t1 = net.insert_node(3);
  auto t2 = net.insert_node(4);
 
  net.insert_arc(s1, t1, 5, 0);
  net.insert_arc(s2, t2, 7, 0);
 
  EXPECT_EQ(net.get_sink_nodes().size(), 2U);
 
  const auto before_nodes = net.get_num_nodes();
  net.make_super_sink();
 
  EXPECT_EQ(net.get_sink_nodes().size(), 1U);
  EXPECT_EQ(net.get_num_nodes(), before_nodes + 1);
 
  auto super_sink = net.get_sink();
  EXPECT_EQ(net.get_in_degree(super_sink), 2U);
 
  bool has_self = false;
  for (Node_Arc_Iterator<Net> it(super_sink); it.has_curr(); it.next_ne())
    {
      if (it.get_tgt_node_ne() == super_sink)
        has_self = true;
    }
  EXPECT_FALSE(has_self);
 
  net.unmake_super_sink();
  EXPECT_EQ(net.get_num_nodes(), before_nodes);
  EXPECT_EQ(net.get_sink_nodes().size(), 2U);
}
 
TEST(NetGraphFlowAlgorithms, FordFulkersonAndEdmondsKarp)
{
  Net net1;
  build_simple_net(net1);
  EXPECT_EQ(ford_fulkerson_maximum_flow(net1), 5);
  EXPECT_TRUE(net1.check_network());
  EXPECT_EQ(net1.flow_value(), 5);
 
  Net net2;
  build_simple_net(net2);
  EXPECT_EQ(edmonds_karp_maximum_flow(net2), 5);
  EXPECT_TRUE(net2.check_network());
  EXPECT_EQ(net2.flow_value(), 5);
}
 
TEST(NetGraphFlowAlgorithms, PreflowVariants)
{
  Net net1;
  build_simple_net(net1);
  EXPECT_EQ(fifo_preflow_maximum_flow(net1), 5);
  EXPECT_TRUE(net1.check_network());
 
  Net net2;
  build_simple_net(net2);
  EXPECT_EQ(heap_preflow_maximum_flow(net2), 5);
  EXPECT_TRUE(net2.check_network());
 
  Net net3;
  build_simple_net(net3);
  EXPECT_EQ(random_preflow_maximum_flow(net3), 5);
  EXPECT_TRUE(net3.check_network());
}
 
TEST(NetGraphAugmentingPaths, IncreaseFlowOnPath)
{
  Net net;
  auto nodes = build_single_arc(net, 4);
 
  auto path = find_aumenting_path_dfs(net, 0);
  auto slack = increase_flow(net, path);
 
  EXPECT_EQ(slack, 4);
  EXPECT_EQ(nodes.st->flow, 4);
}
 
TEST(NetGraphAugmentingPaths, SemiPathAndIncreaseFlow)
{
  Net net;
  auto nodes = build_single_arc(net, 4);
 
  Find_Aumenting_Path_DFS<Net> finder(net);
  DynList<Parc<Net>> semi_path;
  auto slack = finder.semi_path(nodes.s, nodes.t, semi_path, 0);
 
  EXPECT_EQ(slack, 4);
  EXPECT_FALSE(semi_path.is_empty());
 
  increase_flow(net, semi_path, slack);
  EXPECT_EQ(nodes.st->flow, 4);
}
 
TEST(NetGraphResidualHelpers, RemainingFlowAndFilter)
{
  Net net;
  auto nodes = build_single_arc(net, 10, 3);
 
  EXPECT_FALSE(is_residual<Net>(nodes.s, nodes.st));
  EXPECT_TRUE(is_residual<Net>(nodes.t, nodes.st));
  EXPECT_EQ(remaining_flow<Net>(nodes.s, nodes.st), 7);
  EXPECT_EQ(remaining_flow<Net>(nodes.t, nodes.st), 3);
 
  Net_Filt<Net> from_src(nodes.s);
  Net_Filt<Net> from_tgt(nodes.t);
  EXPECT_TRUE(from_src(nodes.st));
  EXPECT_TRUE(from_tgt(nodes.st));
 
  nodes.st->flow = nodes.st->cap;
  EXPECT_FALSE(from_src(nodes.st));
 
  nodes.st->flow = 0;
  EXPECT_FALSE(from_tgt(nodes.st));
}
 
TEST(NetGraphResidualNet, UpdateFlowFromResidual)
{
  Net net;
  build_single_arc(net, 10, 4);
 
  auto residual = preflow_create_residual_net(net);
  auto &rnet = std::get<0>(residual);
  using Rnet = PP_Res_Net<Net>;
 
  Net::Arc *original = nullptr;
  for (typename Rnet::Arc_Iterator it(rnet); it.has_curr(); it.next_ne())
    {
      auto arc = it.get_curr();
      if (arc->img != nullptr)
        {
          original = arc->img;
          arc->flow = 7;
          break;
        }
    }
 
  ASSERT_NE(original, nullptr);
  update_flow(rnet);
  EXPECT_EQ(original->flow, 7);
}
 
TEST(NetGraphMinCut, ComputesCutCapacity)
{
  Net net;
  auto nodes = build_simple_net(net);
 
  DynSetTree<Net::Node *> vs;
  DynSetTree<Net::Node *> vt;
  DynList<Net::Arc *> cuts;
  DynList<Net::Arc *> cutt;
 
  auto value = min_cut<Net, Edmonds_Karp_Maximum_Flow>(net, vs, vt, cuts, cutt);
  EXPECT_EQ(value, 5);
  EXPECT_TRUE(vs.contains(nodes.s));
  EXPECT_TRUE(vt.contains(nodes.t));
 
  int cut_cap = 0;
  for (typename DynList<Net::Arc *>::Iterator it(cuts); it.has_curr(); it.next_ne())
    cut_cap += it.get_curr()->cap;
 
  EXPECT_EQ(cut_cap, value);
}