如何快速写出一个排位榜

发表于2017-03-10
评论3 3.5k浏览

导语 
  在游戏中,除了按数值的排行榜,另一个比较常见的就是排位榜了:和对方竞赛,如果赢了,交换排名;如果输了,保持排名不变。最近因为全民农场有一个拼车的任务,突发奇想就想写一个排位榜的实现,下面就来给大家分享下我是如何快速写出一个排位榜的。

一、目的
  在游戏中,除了按数值的排行榜,另一个比较常见的就是排位榜了:和对方竞赛,如果赢了,交换排名;如果输了,保持排名不变。最近因为全民农场有一个拼车的任务,突发奇想就想写一个排位榜的实现,下面就来给大家分享下我是如何快速写出一个排位榜的。

二、原理
  排位榜应该有如下功能
  1、交换排名
  2、添加排名
  3、通过排名查询到玩家信息
  4、通过玩家帐号查到排名

  鉴于此,我们采用boost::multi_index_container库,采用random_access索引类型做为排名索引,采用ordered_unique做为帐号索引。实现了上述功能,排名的持久化通过boost::interprocessCKV实现:整个排位榜放到内存映射文件里,排位的前N名存到CKV里,通过版本号决定是不是需要从CKV里加载数据。

三、性能
  在现网有4个榜,每个榜5W(做为一个活动,每个区玩的人大概这么多)CPU没有压力。
  分析下数据结构的时间复杂度:我们知道ordered_unique采用红黑树实现,因此添加排名是O(log(N))的,交换排名是O(1)(交换数据就可以了),这个索引开销不会大,random_access_index也可以交换元素(当然在代码里没这么做,不过没有关系),所以效率应该不是问题。

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#pragma once
 
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
#include
 
namespace bmi = boost::multi_index;
namespace bi = boost::interprocess;
 
typedef boost::array<char, 40=""> lpod_open_id_t;
 
class swap_ranker
{
public:
    enum ecode
    {
        e_success = 0,
        e_unknown = -1,
        e_reach_max_num = -2,
        e_duplicate_open_id = -3,
        e_open_id_not_found = -4,
    };
 
    typedef bi::basic_managed_mapped_file<char, bi::rbtree_best_fit"">, bi::iset_index> managed_mapped_file_t;
 
    typedef bi::allocator<char, managed_mapped_file_t::segment_manager="">      char_allocator_t;
    typedef bi::basic_string<char, std::char_traits<char="">, char_allocator_t> char_string_t;
 
    struct node_info
    {
        node_info(const lpod_open_id_t& open_id, char_allocator_t alloc):open_id(open_id), data(alloc){}
        lpod_open_id_t open_id;
        char_string_t data;
    };
 
    typedef bi::node_allocator""> node_info_allocator_t;
 
    struct tag_open_id{};
 
    struct tag_index{};
 
    typedef bmi::multi_index_container<
        node_info,
        bmi::indexed_by<
            bmi::ordered_unique"" &node_info::open_id=""> >,
            bmi::random_access
        >,
        node_info_allocator_t
    > node_info_db_t;
 
 
    typedef node_info_db_t::index::type open_id_index_t;
 
    typedef node_info_db_t::index::type index_index_t;
 
    int init(const std::string& fn, size_t fsize, size_t max_num);
 
    int append(const lpod_open_id_t& open_id, const char* data, int data_len);
 
    int update(const lpod_open_id_t& open_id, const char* data, int data_len);
 
    int swap(const lpod_open_id_t& open_id_a,
        const char* data_a, int data_a_len,
        const lpod_open_id_t& open_id_b,
        const char* data_b, int data_b_len);
 
    inline size_t size() const {return m_db->size();}
 
    const node_info* find_node_info_by_index(int idx) const;
 
    int find_index_by_open_id(const lpod_open_id_t& open_id) const;
 
    uint32_t get_version() const;
 
    void set_version(uint32_t version);
 
private:
    boost::shared_ptr m_file;
    node_info_db_t* m_db;
    size_t m_max_num;
    uint32_t* m_version;
};char,>char,>char,>char,>string>


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#include "swap_ranker.h"
 
int swap_ranker::init(const std::string& fn, size_t fsize, size_t max_num)
{
    m_file.reset(new managed_mapped_file_t(bi::open_or_create, fn.c_str(), fsize));
 
    node_info_allocator_t alloc(m_file->get_segment_manager());
    m_db = m_file->find_or_construct("node_info_db")(alloc);
 
    m_max_num = max_num;
 
    m_db->get().reserve(m_max_num);
 
    m_version = m_file->find_or_construct("version")(0);
 
    return e_success;
}
 
int swap_ranker::append(const lpod_open_id_t& open_id, const char* data, int data_len)
{
    if (m_db->size() >= m_max_num)
    {
        // full
        return e_reach_max_num;
    }
 
    char_allocator_t alloc(m_file->get_segment_manager());
    node_info info(open_id, alloc);
    info.open_id = open_id;
    if (data != NULL && data_len > 0)
    {
        info.data.assign(data, data_len);
    }
    if (!m_db->insert(info).second)
    {
        return e_duplicate_open_id;
    }
 
    return e_success;
}
 
struct node_info_modifier
{
    node_info_modifier(const lpod_open_id_t& open_id, const char* data, int data_len):open_id(open_id), data(data), data_len(data_len){}
    bool operator()(swap_ranker::node_info& info)
    {
        info.open_id = open_id;
        info.data.assign(data, data_len);
        return true;
    }
    lpod_open_id_t open_id;
    const char* data;
    int data_len;
};
 
 
 
int swap_ranker::update(const lpod_open_id_t& open_id, const char* data, int data_len)
{
    open_id_index_t& index = m_db->get();
    open_id_index_t::iterator it = index.find(open_id);
    if (it == index.end())
    {
        return append(open_id, data, data_len);
    }
      
    index.modify(it, node_info_modifier(open_id, data, data_len));
    return e_success;
}
 
extern void print_rank(const swap_ranker& ranker);
 
int swap_ranker::swap(const lpod_open_id_t& open_id_a,
        const char* data_a, int data_a_len,
        const lpod_open_id_t& open_id_b,
        const char* data_b, int data_b_len)
{
    if (open_id_a == open_id_b)
    {
        return e_success;
    }
 
    open_id_index_t& index = m_db->get();
    index_index_t& iindex = m_db->get();
 
    append(open_id_a, data_a, data_a_len);
    append(open_id_b, data_b, data_b_len);
 
    index_index_t::iterator ita = m_db->project"">(index.find(open_id_a));
    index_index_t::iterator itb = m_db->project"">(index.find(open_id_b));
 
    if (ita != iindex.end())
    {
        if (itb != iindex.end())
        {
            index_index_t::iterator ita_next = ita + 1;
            index_index_t::iterator itb_next = itb + 1;
            iindex.relocate(ita_next, itb);
            iindex.relocate(itb_next, ita);
        }
        else
        {
            iindex.modify(ita, node_info_modifier(open_id_b, data_b, data_b_len));
        }
    }
    else
    {
        if (itb != iindex.end())
        {
            iindex.modify(itb, node_info_modifier(open_id_a, data_a, data_a_len));
        }
        else
        {
            // all not on board, nothing todo.
        }
    }
     
    return e_success;
}
 
const swap_ranker::node_info* swap_ranker::find_node_info_by_index(int idx) const
{
    if ((size_t)idx >= size())
    {
        return NULL;
    }
    index_index_t& index = m_db->get();
    return &index[idx];
}
 
int swap_ranker::find_index_by_open_id(const lpod_open_id_t& open_id) const
{
    open_id_index_t& index = m_db->get();
    index_index_t& iindex = m_db->get();
    index_index_t::const_iterator it = m_db->project"">(index.find(open_id));
    if (it != iindex.end())
    {
        return it - iindex.begin();
    }
    else
    {
        return -1;
    }
}
 
 
uint32_t swap_ranker::get_version() const
{
    return *m_version;
}
 
void swap_ranker::set_version(uint32_t version)
{
    *m_version = version;
}

以上就是通过代码快速实现一个排位榜的教程,希望可以帮到大家。

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