java-topology/defects/megaglest-0001/test/test_attack_boost_lookup.cpp

// Unit test for megaglest-0001: Attack boost unit membership lookup
// Defect: std::find on vector<int> inside per-frame loop = O(C * B)
// Fix: std::unordered_set<int> for O(1) membership test
//
// Simulates our attack boost update loop where we check if each candidate
// unit is already in our boosted-units list, and check if each boosted unit
// is still a valid candidate.

#include <algorithm>
#include <cassert>
#include <chrono>
#include <cstdio>
#include <unordered_set>
#include <vector>

// --- DEFECTIVE: O(C * B) linear scan ---
struct AttackBoostDefective {
    std::vector<int> currentAttackBoostUnits;

    void updateBoost(const std::vector<int> &candidateIds) {
        std::vector<int> candidateValidIdList;
        candidateValidIdList.reserve(candidateIds.size());

        for (size_t i = 0; i < candidateIds.size(); ++i) {
            int id = candidateIds[i];
            candidateValidIdList.push_back(id);

            // O(B) linear scan per candidate
            auto iterFound = std::find(currentAttackBoostUnits.begin(),
                                       currentAttackBoostUnits.end(), id);
            if (iterFound == currentAttackBoostUnits.end()) {
                // New unit: apply boost
                currentAttackBoostUnits.push_back(id);
            }
        }

        // Remove units no longer in range: O(B * C) linear scan
        for (int i = (int)currentAttackBoostUnits.size() - 1; i >= 0; --i) {
            int findUnitId = currentAttackBoostUnits[i];
            auto iterFound = std::find(candidateValidIdList.begin(),
                                       candidateValidIdList.end(), findUnitId);
            if (iterFound == candidateValidIdList.end()) {
                currentAttackBoostUnits.erase(
                    currentAttackBoostUnits.begin() + i);
            }
        }
    }
};

// --- FIXED: O(C + B) with hash sets ---
struct AttackBoostFixed {
    std::vector<int> currentAttackBoostUnits;

    void updateBoost(const std::vector<int> &candidateIds) {
        std::unordered_set<int> candidateValidIdSet;
        candidateValidIdSet.reserve(candidateIds.size());

        // Build hash set of currently boosted IDs for O(1) lookup
        std::unordered_set<int> boostedIdSet(
            currentAttackBoostUnits.begin(),
            currentAttackBoostUnits.end());

        for (size_t i = 0; i < candidateIds.size(); ++i) {
            int id = candidateIds[i];
            candidateValidIdSet.insert(id);

            // O(1) hash lookup
            if (boostedIdSet.count(id) == 0) {
                currentAttackBoostUnits.push_back(id);
                boostedIdSet.insert(id);
            }
        }

        // Remove units no longer in range: O(1) hash lookup per boosted unit
        for (int i = (int)currentAttackBoostUnits.size() - 1; i >= 0; --i) {
            int findUnitId = currentAttackBoostUnits[i];
            if (candidateValidIdSet.count(findUnitId) == 0) {
                currentAttackBoostUnits.erase(
                    currentAttackBoostUnits.begin() + i);
            }
        }
    }
};

// Verify correctness: both produce same result
void test_correctness() {
    printf("test_correctness... ");

    // Initial boosted set
    std::vector<int> initialBoosted = {10, 20, 30, 40, 50};
    // New candidates: some overlap, some new, some old ones gone
    std::vector<int> candidates = {20, 30, 60, 70, 80};

    AttackBoostDefective defective;
    defective.currentAttackBoostUnits = initialBoosted;
    defective.updateBoost(candidates);

    AttackBoostFixed fixed;
    fixed.currentAttackBoostUnits = initialBoosted;
    fixed.updateBoost(candidates);

    // Sort both for comparison
    std::vector<int> defResult = defective.currentAttackBoostUnits;
    std::vector<int> fixResult = fixed.currentAttackBoostUnits;
    std::sort(defResult.begin(), defResult.end());
    std::sort(fixResult.begin(), fixResult.end());

    assert(defResult == fixResult);
    // Should contain: 20, 30, 60, 70, 80 (10, 40, 50 removed; 60, 70, 80 added)
    std::vector<int> expected = {20, 30, 60, 70, 80};
    assert(defResult == expected);

    printf("PASS\n");
}

// Verify empty candidates removes all boosted
void test_empty_candidates() {
    printf("test_empty_candidates... ");

    std::vector<int> initialBoosted = {1, 2, 3, 4, 5};
    std::vector<int> candidates = {};

    AttackBoostDefective defective;
    defective.currentAttackBoostUnits = initialBoosted;
    defective.updateBoost(candidates);

    AttackBoostFixed fixed;
    fixed.currentAttackBoostUnits = initialBoosted;
    fixed.updateBoost(candidates);

    assert(defective.currentAttackBoostUnits.empty());
    assert(fixed.currentAttackBoostUnits.empty());

    printf("PASS\n");
}

// Benchmark: measure O(C*B) vs O(C+B)
void test_performance() {
    printf("test_performance... ");

    const int B = 2000;  // boosted units
    const int C = 2000;  // candidates
    const int ITERS = 20;

    // Build initial boosted list (1..B)
    std::vector<int> initialBoosted;
    for (int i = 1; i <= B; ++i) initialBoosted.push_back(i);

    // Candidates: half overlap (1..C/2), half new (B+1..B+C/2)
    std::vector<int> candidates;
    for (int i = 1; i <= C / 2; ++i) candidates.push_back(i);
    for (int i = B + 1; i <= B + C / 2; ++i) candidates.push_back(i);

    // Defective
    auto t0 = std::chrono::high_resolution_clock::now();
    for (int iter = 0; iter < ITERS; ++iter) {
        AttackBoostDefective d;
        d.currentAttackBoostUnits = initialBoosted;
        d.updateBoost(candidates);
    }
    auto t1 = std::chrono::high_resolution_clock::now();

    // Fixed
    auto t2 = std::chrono::high_resolution_clock::now();
    for (int iter = 0; iter < ITERS; ++iter) {
        AttackBoostFixed f;
        f.currentAttackBoostUnits = initialBoosted;
        f.updateBoost(candidates);
    }
    auto t3 = std::chrono::high_resolution_clock::now();

    double defective_ms = std::chrono::duration<double, std::milli>(t1 - t0).count();
    double fixed_ms = std::chrono::duration<double, std::milli>(t3 - t2).count();
    double ratio = defective_ms / fixed_ms;

    printf("defective=%.1fms fixed=%.1fms ratio=%.1fx ", defective_ms, fixed_ms, ratio);
    assert(ratio > 2.0);
    printf("PASS\n");
}

int main() {
    printf("=== megaglest-0001: Attack boost unit membership O(C*B) -> O(C+B) ===\n");
    test_correctness();
    test_empty_candidates();
    test_performance();
    printf("All tests passed.\n");
    return 0;
}