tpl_multicommodity_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
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  SOFTWARE.
*/
 
 
#include <gtest/gtest.h>
#include <tpl_multicommodity.H>
#include <cmath>
#include <vector>
 
using namespace Aleph;
 
// Type aliases at file scope
using TestNode = Graph_Anode<Empty_Class>;
using TestArc = MCF_Arc<Empty_Class, double>;
using TestNet = MCF_Graph<TestNode, TestArc>;
 
//==============================================================================
// Test Fixture
//==============================================================================
 
class MultiCommodityTest : public ::testing::Test
{
protected:
  static constexpr double EPSILON = 1e-6;
 
  bool nearly_equal(double a, double b, double eps = EPSILON)
  {
    return std::fabs(a - b) < eps;
  }
 
  // Build a simple 2-node network
  TestNet build_single_arc_network(double capacity, double cost)
  {
    TestNet net;
    auto s = net.insert_node();
    auto t = net.insert_node();
    net.insert_arc(s, t, capacity, cost);
    return net;
  }
 
  // Build a diamond network
  TestNet build_diamond_network()
  {
    TestNet net;
    auto s = net.insert_node();
    auto a = net.insert_node();
    auto b = net.insert_node();
    auto t = net.insert_node();
 
    net.insert_arc(s, a, 10.0, 1.0);
    net.insert_arc(s, b, 10.0, 2.0);
    net.insert_arc(a, t, 10.0, 1.0);
    net.insert_arc(b, t, 10.0, 2.0);
 
    return net;
  }
 
  // Build a parallel paths network
  TestNet build_parallel_paths()
  {
    TestNet net;
    auto s = net.insert_node();
    auto a = net.insert_node();
    auto b = net.insert_node();
    auto t = net.insert_node();
 
    net.insert_arc(s, a, 5.0, 1.0);
    net.insert_arc(a, t, 5.0, 1.0);
    net.insert_arc(s, b, 5.0, 2.0);
    net.insert_arc(b, t, 5.0, 2.0);
 
    return net;
  }
};
 
//==============================================================================
// Basic Structure Tests
//==============================================================================
 
TEST_F(MultiCommodityTest, EmptyNetwork)
{
  TestNet net;
  EXPECT_EQ(net.vsize(), 0);
  EXPECT_EQ(net.esize(), 0);
  EXPECT_EQ(net.num_commodities(), 0);
}
 
TEST_F(MultiCommodityTest, InsertNodesAndArcs)
{
  TestNet net;
  auto s = net.insert_node();
  auto t = net.insert_node();
  auto arc = net.insert_arc(s, t, 10.0, 5.0);
 
  EXPECT_EQ(net.vsize(), 2);
  EXPECT_EQ(net.esize(), 1);
  EXPECT_EQ(arc->capacity, 10.0);
  EXPECT_EQ(arc->base_cost, 5.0);
}
 
TEST_F(MultiCommodityTest, AddCommodity)
{
  auto net = build_single_arc_network(10.0, 1.0);
 
  auto nodes = net.nodes();
  auto it = nodes.get_it();
  auto s = it.get_curr(); it.next();
  auto t = it.get_curr();
 
  size_t k = net.add_commodity(s, t, 5.0, "Commodity 1");
 
  EXPECT_EQ(k, 0);
  EXPECT_EQ(net.num_commodities(), 1);
 
  const auto& comm = net.get_commodity(0);
  EXPECT_EQ(comm.source, s);
  EXPECT_EQ(comm.sink, t);
  EXPECT_EQ(comm.demand, 5.0);
  EXPECT_EQ(comm.name, "Commodity 1");
}
 
TEST_F(MultiCommodityTest, ArcFlowPerCommodity)
{
  TestNet net;
  auto s = net.insert_node();
  auto t = net.insert_node();
  auto arc = net.insert_arc(s, t, 20.0, 1.0);
 
  net.add_commodity(s, t, 5.0);
  net.add_commodity(s, t, 8.0);
 
  arc->set_flow(0, 5.0);
  arc->set_flow(1, 8.0);
 
  EXPECT_EQ(arc->flow(0), 5.0);
  EXPECT_EQ(arc->flow(1), 8.0);
  EXPECT_EQ(arc->total_flow(), 13.0);
  EXPECT_EQ(arc->residual(), 7.0);
}
 
TEST_F(MultiCommodityTest, MultipleCommodities)
{
  auto net = build_diamond_network();
 
  auto nodes = net.nodes();
  auto it = nodes.get_it();
  auto s = it.get_curr(); it.next();
  it.next(); it.next();
  auto t = it.get_curr();
 
  net.add_commodity(s, t, 5.0, "K1");
  net.add_commodity(s, t, 3.0, "K2");
 
  EXPECT_EQ(net.num_commodities(), 2);
  EXPECT_EQ(net.get_commodity(0).demand, 5.0);
  EXPECT_EQ(net.get_commodity(1).demand, 3.0);
}
 
//==============================================================================
// Solver Tests - Single Commodity
//==============================================================================
 
TEST_F(MultiCommodityTest, SingleCommoditySingleArc)
{
  auto net = build_single_arc_network(10.0, 2.0);
 
  auto nodes = net.nodes();
  auto it = nodes.get_it();
  auto s = it.get_curr(); it.next();
  auto t = it.get_curr();
 
  net.add_commodity(s, t, 5.0);
 
  auto result = solve_multicommodity_flow(net);
 
  EXPECT_TRUE(result.is_optimal());
  EXPECT_NEAR(result.total_cost, 10.0, 0.1);  // 5 * 2 = 10
}
 
TEST_F(MultiCommodityTest, SingleCommodityDiamond)
{
  auto net = build_diamond_network();
 
  auto nodes = net.nodes();
  auto it = nodes.get_it();
  auto s = it.get_curr(); it.next();
  it.next(); it.next();
  auto t = it.get_curr();
 
  net.add_commodity(s, t, 5.0);
 
  auto result = solve_multicommodity_flow(net);
 
  EXPECT_TRUE(result.is_optimal());
  EXPECT_NEAR(result.total_cost, 10.0, 1.0);
}
 
TEST_F(MultiCommodityTest, SingleCommodityParallelPaths)
{
  auto net = build_parallel_paths();
 
  auto nodes = net.nodes();
  auto it = nodes.get_it();
  auto s = it.get_curr(); it.next();
  it.next(); it.next();
  auto t = it.get_curr();
 
  net.add_commodity(s, t, 8.0);
 
  auto result = solve_multicommodity_flow(net);
 
  EXPECT_TRUE(result.is_optimal());
  EXPECT_GT(result.total_cost, 0.0);
}
 
//==============================================================================
// Solver Tests - Multiple Commodities
//==============================================================================
 
TEST_F(MultiCommodityTest, TwoCommoditiesCompeting)
{
  TestNet net;
  auto s1 = net.insert_node();
  auto s2 = net.insert_node();
  auto m = net.insert_node();
  auto t1 = net.insert_node();
  auto t2 = net.insert_node();
 
  net.insert_arc(s1, m, 10.0, 1.0);
  net.insert_arc(s2, m, 10.0, 1.0);
  net.insert_arc(m, t1, 5.0, 1.0);
  net.insert_arc(m, t2, 5.0, 1.0);
 
  net.add_commodity(s1, t1, 3.0, "K1");
  net.add_commodity(s2, t2, 3.0, "K2");
 
  auto result = solve_multicommodity_flow(net);
 
  EXPECT_TRUE(result.is_optimal());
  EXPECT_GT(result.total_cost, 0.0);
}
 
TEST_F(MultiCommodityTest, TwoCommoditiesSharedCapacity)
{
  TestNet net;
  auto s = net.insert_node();
  auto t = net.insert_node();
 
  auto arc = net.insert_arc(s, t, 10.0, 1.0);
 
  net.add_commodity(s, t, 4.0, "K1");
  net.add_commodity(s, t, 4.0, "K2");
 
  auto result = solve_multicommodity_flow(net);
 
  EXPECT_TRUE(result.is_optimal());
  EXPECT_NEAR(result.total_cost, 8.0, 0.1);
 
  EXPECT_NEAR(arc->flow(0), 4.0, 0.1);
  EXPECT_NEAR(arc->flow(1), 4.0, 0.1);
  EXPECT_NEAR(arc->total_flow(), 8.0, 0.1);
}
 
TEST_F(MultiCommodityTest, ThreeCommodities)
{
  auto net = build_diamond_network();
 
  auto nodes = net.nodes();
  auto it = nodes.get_it();
  auto s = it.get_curr(); it.next();
  it.next(); it.next();
  auto t = it.get_curr();
 
  net.add_commodity(s, t, 2.0, "K1");
  net.add_commodity(s, t, 3.0, "K2");
  net.add_commodity(s, t, 4.0, "K3");
 
  auto result = solve_multicommodity_flow(net);
 
  EXPECT_TRUE(result.is_optimal());
  EXPECT_GT(result.total_cost, 0.0);
}
 
//==============================================================================
// Edge Cases
//==============================================================================
 
TEST_F(MultiCommodityTest, ZeroDemand)
{
  auto net = build_single_arc_network(10.0, 1.0);
 
  auto nodes = net.nodes();
  auto it = nodes.get_it();
  auto s = it.get_curr(); it.next();
  auto t = it.get_curr();
 
  net.add_commodity(s, t, 0.0);
 
  auto result = solve_multicommodity_flow(net);
 
  EXPECT_TRUE(result.is_optimal());
  EXPECT_NEAR(result.total_cost, 0.0, 0.1);
}
 
TEST_F(MultiCommodityTest, NoCommodities)
{
  auto net = build_diamond_network();
 
  auto result = solve_multicommodity_flow(net);
 
  EXPECT_TRUE(result.is_optimal());
  EXPECT_NEAR(result.total_cost, 0.0, 0.1);
}
 
//==============================================================================
// Validation Tests
//==============================================================================
 
TEST_F(MultiCommodityTest, CapacityRespected)
{
  TestNet net;
  auto s = net.insert_node();
  auto t = net.insert_node();
  net.insert_arc(s, t, 10.0, 1.0);
 
  net.add_commodity(s, t, 4.0);
  net.add_commodity(s, t, 5.0);
 
  auto result = solve_multicommodity_flow(net);
 
  EXPECT_TRUE(result.is_optimal());
  EXPECT_TRUE(net.capacities_respected());
}
 
TEST_F(MultiCommodityTest, DifferentCostsPerCommodity)
{
  TestNet net;
  auto s = net.insert_node();
  auto t = net.insert_node();
  auto arc = net.insert_arc(s, t, 20.0, 1.0);  // base cost = 1
 
  // Add commodities FIRST, then set per-commodity costs
  net.add_commodity(s, t, 3.0, "Cheap");       // k=0
  net.add_commodity(s, t, 2.0, "Expensive");   // k=1
 
  // Now set different costs per commodity
  arc->set_cost(0, 1.0);  // Commodity 0: cost 1
  arc->set_cost(1, 5.0);  // Commodity 1: cost 5
 
  auto result = solve_multicommodity_flow(net);
 
  // Expected: 3 * 1 + 2 * 5 = 13
  EXPECT_TRUE(result.is_optimal());
  EXPECT_NEAR(result.total_cost, 13.0, 0.1);
}
 
//==============================================================================
// Performance Test
//==============================================================================
 
TEST_F(MultiCommodityTest, MediumNetwork)
{
  const int grid_size = 4;
  TestNet mcf_net;
 
  std::vector<TestNode*> grid_nodes;
  grid_nodes.reserve(grid_size * grid_size);
 
  for (int i = 0; i < grid_size * grid_size; ++i)
    grid_nodes.push_back(mcf_net.insert_node());
 
  auto node_at = [&](int i, int j) { return grid_nodes[i * grid_size + j]; };
 
  for (int i = 0; i < grid_size; ++i)
    {
      for (int j = 0; j < grid_size; ++j)
        {
          if (j + 1 < grid_size)
            mcf_net.insert_arc(node_at(i, j), node_at(i, j + 1), 5.0, 1.0);
          if (i + 1 < grid_size)
            mcf_net.insert_arc(node_at(i, j), node_at(i + 1, j), 5.0, 1.0);
        }
    }
 
  mcf_net.add_commodity(node_at(0, 0), node_at(grid_size-1, grid_size-1),
                        2.0, "TopLeft-BottomRight");
  mcf_net.add_commodity(node_at(0, grid_size-1), node_at(grid_size-1, 0),
                        2.0, "TopRight-BottomLeft");
 
  auto result = solve_multicommodity_flow(mcf_net);
 
  std::cout << "Grid " << grid_size << "x" << grid_size << ": "
            << "cost=" << result.total_cost
            << ", time=" << result.solve_time_ms << " ms"
            << ", iterations=" << result.iterations << "\n";
 
  EXPECT_TRUE(result.is_optimal());
  EXPECT_GT(result.total_cost, 0.0);
}
 
//==============================================================================
// Result Structure Tests
//==============================================================================
 
TEST_F(MultiCommodityTest, ResultStructure)
{
  TestNet net;
  auto s = net.insert_node();
  auto a = net.insert_node();
  auto b = net.insert_node();
  auto t = net.insert_node();
 
  net.insert_arc(s, a, 10.0, 1.0);
  net.insert_arc(s, b, 10.0, 2.0);
  net.insert_arc(a, t, 10.0, 1.0);
  net.insert_arc(b, t, 10.0, 2.0);
 
  net.add_commodity(s, t, 5.0, "K1");
  net.add_commodity(s, t, 3.0, "K2");
 
  auto result = solve_multicommodity_flow(net);
 
  EXPECT_TRUE(result.is_optimal());
  EXPECT_EQ(result.commodity_costs.size(), 2u);
  EXPECT_GE(result.solve_time_ms, 0.0);
  EXPECT_GT(result.iterations, 0u);
 
  double sum = 0;
  for (auto c : result.commodity_costs)
    sum += c;
  EXPECT_NEAR(sum, result.total_cost, 0.1);
}
 
int main(int argc, char **argv)
{
  ::testing::InitGoogleTest(&argc, argv);
  return RUN_ALL_TESTS();
}