ftsp算法C语言实现

FTSP (Flooding Time Synchronization Protocol) 是一种分布式的时间同步协议，适用于无线传感器网络中的节点之间进行时间同步。以下是 FTSP 算法的 C 语言实现：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <math.h>
#include <time.h>

// 定义 FTSP 协议中用到的常量
#define MAX_MSG 10              // 最大消息数
#define MAX_NEIGHBORS 10        // 最大邻居节点数
#define MESSAGE_HELLO 0         // HELLO 消息类型
#define MESSAGE_SYNC 1          // SYNC 消息类型
#define MESSAGE_SYNC_ACK 2      // SYNC_ACK 消息类型
#define ROOT_ID 0              // 根节点的 ID
#define ROUND_DURATION 1        // 一轮时间的长度（单位为秒）
#define MAX_ROUND_ERROR 0.1     // 最大轮间误差（单位为秒）

// 定义消息的结构体
typedef struct _message {
    int src;                    // 源节点 ID
    int dest;                   // 目标节点 ID
    int type;                   // 消息类型
    double timestamp;           // 时间戳
} message_t;

// 定义节点的结构体
typedef struct _node {
    int id;                     // 节点 ID
    int neighbors[MAX_NEIGHBORS];  // 邻居节点的 ID 列表
    int num_neighbors;          // 邻居节点数
    double clock_offset;        // 时钟偏差
    double clock_skew;          // 时钟漂移
    double round_start_time;    // 当前轮的起始时间
    double round_time_offset;   // 当前轮的时间偏移
    double round_skew;          // 当前轮的时钟漂移
} node_t;

// 定义全局变量
int num_nodes;                  // 节点数
node_t *nodes;                  // 节点列表
message_t messages[MAX_MSG];    // 消息列表
int num_messages;               // 消息数
int root_id = ROOT_ID;          // 根节点 ID

// 定义消息发送函数
void send_message(int src, int dest, int type, double timestamp) {
    if (num_messages < MAX_MSG) {
        messages[num_messages].src = src;
        messages[num_messages].dest = dest;
        messages[num_messages].type = type;
        messages[num_messages].timestamp = timestamp;
        num_messages++;
    }
}

// 定义消息处理函数
void process_message(int node_id, message_t *msg) {
    node_t *node = &nodes[node_id];
    double timestamp = msg->timestamp;
    double time_diff = 0;
    double delay = 0;
    int i;

    switch (msg->type) {
        case MESSAGE_HELLO:
            // 处理 HELLO 消息
            if (node_id != root_id) {
                send_message(node_id, root_id, MESSAGE_HELLO, timestamp);
            }
            break;
        case MESSAGE_SYNC:
            // 处理 SYNC 消息
            delay = (double)(rand() % 1000) / 1000.0; // 模拟传输延迟
            timestamp += delay;
            time_diff = timestamp - node->round_start_time;
            if (node_id == root_id) {
                // 如果是根节点，则直接回复 SYNC_ACK 消息
                send_message(root_id, msg->src, MESSAGE_SYNC_ACK, timestamp);
            } else {
                // 如果不是根节点，则将 SYNC 消息转发给所有邻居节点
                for (i = 0; i < node->num_neighbors; i++) {
                    send_message(node_id, node->neighbors[i], MESSAGE_SYNC, timestamp);
                }
                // 更新时钟偏差和时钟漂移
                node->clock_offset = (time_diff + msg->timestamp - node->round_start_time) / 2.0;
                node->clock_skew = (time_diff - node->clock_offset) / ROUND_DURATION;
            }
            break;
        case MESSAGE_SYNC_ACK:
            // 处理 SYNC_ACK 消息
            delay = (double)(rand() % 1000) / 1000.0; // 模拟传输延迟
            timestamp += delay;
            time_diff = timestamp - node->round_start_time;
            // 更新时钟偏差和时钟漂移
            node->clock_offset = (time_diff + msg->timestamp - node->round_start_time) / 2.0;
            node->clock_skew = (time_diff - node->clock_offset) / ROUND_DURATION;
            break;
        default:
            break;
    }
}

// 定义主函数
int main(int argc, char **argv) {
    int i, j;
    double round_duration = ROUND_DURATION;
    double max_round_error = MAX_ROUND_ERROR;
    double round_start_time = 0;
    double round_time_offset = 0;
    double round_skew = 0;
    double current_time = 0;
    double next_round_time = 0;
    double next_hello_time = 0;
    double error = 0;
    int num_sync = 0;
    int num_sync_ack = 0;
    int root_sync = 0;

    // 初始化随机数生成器
    srand(time(NULL));

    // 读取节点数和邻接矩阵
    scanf("%d", &num_nodes);
    nodes = (node_t*)malloc(num_nodes * sizeof(node_t));
    for (i = 0; i < num_nodes; i++) {
        nodes[i].id = i;
        nodes[i].num_neighbors = 0;
        nodes[i].clock_offset = 0;
        nodes[i].clock_skew = 0;
        nodes[i].round_start_time = 0;
        nodes[i].round_time_offset = 0;
        nodes[i].round_skew = 0;
        for (j = 0; j < num_nodes; j++) {
            int is_neighbor;
            scanf("%d", &is_neighbor);
            if (is_neighbor) {
                nodes[i].neighbors[nodes[i].num_neighbors] = j;
                nodes[i].num_neighbors++;
            }
        }
    }

    // 发送初始 HELLO 消息
    for (i = 0; i < num_nodes; i++) {
        send_message(i, root_id, MESSAGE_HELLO, 0);
    }

    // 开始时间同步
    while (1) {
        // 发送 HELLO 消息
        if (current_time >= next_hello_time) {
            for (i = 0; i < num_nodes; i++) {
                send_message(i, root_id, MESSAGE_HELLO, current_time);
            }
            next_hello_time = current_time + 1.0;
        }

        // 处理消息
        for (i = 0; i < num_messages; i++) {
            message_t *msg = &messages[i];
            if (msg->dest == root_id) {
                // 如果是根节点，则直接处理消息
                process_message(msg->src, msg);
            } else {
                // 如果不是根节点，则将消息转发给目标节点
                send_message(msg->src, msg->dest, msg->type, msg->timestamp);
            }
        }
        num_messages = 0;

        // 计算当前轮的时间偏移和时钟漂移
        if (current_time >= next_round_time) {
            // 计算当前轮的起始时间
            if (root_sync) {
                round_start_time = next_round_time - round_time_offset - round_skew * ROUND_DURATION;
            } else {
                round_start_time = next_round_time;
            }
            for (i = 0; i < num_nodes; i++) {
                node_t *node = &nodes[i];
                if (node->id == root_id) {
                    node->round_start_time = round_start_time;
                    node->round_time_offset = round_time_offset;
                    node->round_skew = round_skew;
                } else {
                    node->round_start_time = round_start_time;
                    node->round_time_offset = node->clock_offset + node->round_skew * ROUND_DURATION;
                    node->round_skew = node->clock_skew;
                }
            }
            // 发送 SYNC 消息
            for (i = 0; i < num_nodes; i++) {
                node_t *node = &nodes[i];
                if (node->id == root_id) {
                    // 如果是根节点，则等待所有节点回复 SYNC_ACK 消息
                    num_sync = 0;
                    num_sync_ack = 0;
                    for (j = 0; j < node->num_neighbors; j++) {
                        send_message(root_id, node->neighbors[j], MESSAGE_SYNC, round_start_time);
                        num_sync++;
                    }
                    root_sync = 1;
                } else {
                    // 如果不是根节点，则发送 SYNC 消息并等待回复 SYNC_ACK 消息
                    send_message(node->id, root_id, MESSAGE_SYNC, round_start_time);
                    num_sync++;
                }
            }
            // 等待 SYNC_ACK 消息
            while (num_sync_ack < num_sync) {
                for (i = 0; i < num_messages; i++) {
                    message_t *msg = &messages[i];
                    if (msg->type == MESSAGE_SYNC_ACK) {
                        process_message(msg->dest, msg);
                        num_sync_ack++;
                    }
                }
                num_messages = 0;
            }
            // 计算时间偏移和时钟漂移的平均值
            round_time_offset = 0;
            round_skew = 0;
            for (i = 0; i < num_nodes; i++) {
                node_t *node = &nodes[i];
                if (node->id == root_id) {
                    round_time_offset += node->round_time_offset;
                    round_skew += node->round_skew;
                } else {
                    round_time_offset += node->round_start_time - node->clock_offset;
                    round_skew += node->clock_skew;
                }
            }
            round_time_offset /= (double)num_nodes;
            round_skew /= (double)num_nodes;
            // 检查轮间误差是否超过了最大值
            error = round_start_time - next_round_time;
            if (error > max_round_error) {
                round_duration -= 0.1;
            } else if (error < -max_round_error) {
                round_duration += 0.1;
            }
            // 更新下一轮的起始时间
            next_round_time += round_duration;
            root_sync = 0;
        }

        // 更新当前时间
        current_time += 0.01;
    }

    return 0;
}

注意：以上代码仅供参考，实际使用时需要根据具体需求进行修改和优化。