commit 87dce7e59f1f0c14a8dfed426bfde419664ae55b Author: Yang Huiting <3552600665@qq.com> Date: Wed Mar 25 10:46:44 2026 +0800 chushihua diff --git a/shangji.cpp b/shangji.cpp new file mode 100644 index 0000000..51623ce --- /dev/null +++ b/shangji.cpp @@ -0,0 +1,225 @@ +#include +#include +#include +#include + +// 全局变量 +volatile int parking_spot_available = 1; +volatile int turn = 0; +volatile int flag[2] = { 0, 0 }; +volatile int success_count[3] = { 0, 0, 0 }; +volatile int cpu_usage[3] = { 0, 0, 0 }; // CPU占用计数器 +volatile int conflict_count = 0; + +// 算法A：值日法（单标志法） +DWORD WINAPI algorithm_a(LPVOID param) { + int thread_id = (int)param; + int attempts = 40; + for (int i = 0; i < attempts; i++) { + // 繁忙等待 - 等待轮到自己 + while (turn != thread_id) { + cpu_usage[thread_id]++; // 记录CPU占用 + } + // 进入临界区 + if (parking_spot_available) { + Sleep(5); // 模拟使用车位 + success_count[thread_id]++; + parking_spot_available = 0; + parking_spot_available = 1; + } + // 让下一个线程有机会 + turn = (thread_id + 1) % 3; + Sleep(1); + } + return 0; +} + +// 算法B：双标志检查法 +DWORD WINAPI algorithm_b(LPVOID param) { + int thread_id = (int)param; + int attempts = 40; + int local_conflicts = 0; + for (int i = 0; i < attempts; i++) { + int wait_count = 0; + int max_wait = 10000; + // 第一步：设置自己的标志为TRUE + flag[thread_id % 2] = 1; + // 第二步：检查其他线程的标志 + int other_thread = (thread_id + 1) % 3; + while (flag[other_thread % 2] && wait_count < max_wait) { + cpu_usage[thread_id]++; // 记录CPU占用 + wait_count++; + if (wait_count % 1000 == 0) { + Sleep(1); + } + } + if (wait_count >= max_wait) { + flag[thread_id % 2] = 0; + Sleep(10); + continue; + } + // 检查是否违反互斥 + if (!parking_spot_available) { + local_conflicts++; + conflict_count++; + } + // 进入临界区 + if (parking_spot_available) { + Sleep(5); + success_count[thread_id]++; + parking_spot_available = 0; + parking_spot_available = 1; + } + // 离开临界区 + flag[thread_id % 2] = 0; + Sleep(1); + } + return 0; +} + +// 算法C：Peterson算法 +DWORD WINAPI algorithm_c(LPVOID param) { + int thread_id = (int)param; + int attempts = 40; + if (thread_id == 2) { + // 第三个线程使用简单等待 + for (int i = 0; i < attempts; i++) { + while (!parking_spot_available) { + cpu_usage[thread_id]++; // 记录CPU占用 + } + if (parking_spot_available) { + Sleep(5); + success_count[thread_id]++; + parking_spot_available = 0; + parking_spot_available = 1; + } + Sleep(1); + } + return 0; + } + // 线程0和1使用Peterson算法 + for (int i = 0; i < attempts; i++) { + flag[thread_id] = 1; + turn = 1 - thread_id; + while (flag[1 - thread_id] && turn == 1 - thread_id) { + cpu_usage[thread_id]++; // 记录CPU占用 + } + if (parking_spot_available) { + Sleep(5); + success_count[thread_id]++; + parking_spot_available = 0; + parking_spot_available = 1; + } + flag[thread_id] = 0; + Sleep(1); + } + return 0; +} + +// 测试函数 +void test_algorithm(int algorithm_type) { + HANDLE threads[3]; + DWORD threadIDs[3]; + // 重置计数器 + for (int i = 0; i < 3; i++) { + success_count[i] = 0; + cpu_usage[i] = 0; + } + parking_spot_available = 1; + turn = 0; + flag[0] = 0; + flag[1] = 0; + conflict_count = 0; + + printf("\n=== 测试算法 %c ===\n", 'A' + algorithm_type - 1); + + // 创建线程 + for (int i = 0; i < 3; i++) { + switch (algorithm_type) { + case 1: + threads[i] = CreateThread(NULL, 0, algorithm_a, (LPVOID)i, 0, &threadIDs[i]); + break; + case 2: + threads[i] = CreateThread(NULL, 0, algorithm_b, (LPVOID)i, 0, &threadIDs[i]); + break; + case 3: + threads[i] = CreateThread(NULL, 0, algorithm_c, (LPVOID)i, 0, &threadIDs[i]); + break; + } + } + + // 等待所有线程完成 + WaitForMultipleObjects(3, threads, TRUE, INFINITE); + + // 输出结果 + printf("成功抢到次数:\n"); + printf(" 线程0: %d次\n", success_count[0]); + printf(" 线程1: %d次\n", success_count[1]); + printf(" 线程2: %d次\n", success_count[2]); + printf(" 总计: %d次\n", success_count[0] + success_count[1] + success_count[2]); + + printf("\nCPU占用(繁忙等待循环次数):\n"); + printf(" 线程0: %d次\n", cpu_usage[0]); + printf(" 线程1: %d次\n", cpu_usage[1]); + printf(" 线程2: %d次\n", cpu_usage[2]); + printf(" 总计: %d次\n", cpu_usage[0] + cpu_usage[1] + cpu_usage[2]); + + if (conflict_count > 0) { + printf("\n*** 检测到%d次冲突（违反互斥） ***\n", conflict_count); + } + + // 关闭线程句柄 + for (int i = 0; i < 3; i++) { + CloseHandle(threads[i]); + } +} + +int main() { + printf("=== 抢车位模拟实验 - 三种繁忙等待算法对比 ===\n"); + printf("量化指标: 成功抢到次数 & CPU占用(繁忙等待循环次数)\n"); + printf("实验配置: 3个线程，每个线程尝试40次，总共120次\n"); + + // 测试算法A + printf("\n算法A：值日法（单标志法）"); + printf("\n特点：严格轮流，保证互斥但效率低\n"); + test_algorithm(1); + + // 测试算法B + printf("\n算法B：双标志检查法"); + printf("\n特点：可能违反互斥，可能死锁\n"); + test_algorithm(2); + + // 测试算法C + printf("\n算法C：Peterson算法"); + printf("\n特点：保证互斥，不会死锁\n"); + test_algorithm(3); + + // 实验结果分析 + printf("\n=== 实验结果分析 ===\n"); + printf("\n1. 正确性对比（是否违反互斥）:\n"); + printf(" - 算法A: 保证互斥，无冲突\n"); + printf(" - 算法B: 可能违反互斥，出现冲突\n"); + printf(" - 算法C: 保证互斥，无冲突\n"); + + printf("\n2. 公平性对比（成功次数分布）:\n"); + printf(" - 算法A: 严格轮流，最公平\n"); + printf(" - 算法B: 分布不均，可能出现饥饿\n"); + printf(" - 算法C: 相对公平\n"); + + printf("\n3. CPU浪费程度对比（繁忙等待循环次数）:\n"); + printf(" - 算法A: CPU占用最高，浪费严重\n"); + printf(" - 算法B: CPU占用中等，但存在正确性问题\n"); + printf(" - 算法C: CPU占用相对较低，效率较好\n"); + + printf("\n4. 综合评估:\n"); + printf(" - 算法A: 正确性√ 公平性√ 但CPU浪费严重\n"); + printf(" - 算法B: 正确性× 公平性× CPU浪费中等\n"); + printf(" - 算法C: 正确性√ 公平性○ CPU浪费较低\n\n"); + + printf("\n5. 信号量/互斥锁的优势:\n"); + printf(" - 避免繁忙等待，CPU占用大幅降低\n"); + printf(" - 保证正确性和公平性\n"); + printf(" - 现代操作系统推荐使用\n"); + + return 0; +}