by zieckey
测试条件:
gcc version 4.2.1 20070719 [FreeBSD]
FreeBSD 7.2-RELEASE #0: Fri May 1 07:18:07 UTC 2009 root@driscoll.cse.buffalo.edu:/usr/obj/usr/src/sys/GENERIC amd64
Intel(R) Xeon(R) CPU E5620 @ 2.40GHz 16核
测试程序说明:
先准备好n个字符串随机的MD5字符串做为key,然后分别对3个容器进行插入、遍历、查找、删除操作。
例如,n=100的时候,插入是指插入100个随机MD5 key;遍历是指对容器遍历一次;查找是指分别对这个100个随机的MD5 key做查找操作(即查找100次);删除是指挨个删除这个100个随机MD5 key。
测试数据如下表:
插入,单位us | 100 | 1K | 10K | 100K | 1M | 10M |
std::map | 241 | 2833 | 35888 | 381214 | 4439088 | 62233380 |
std::ext/hash_map | 97 | 1667 | 16466 | 146025 | 1788446 | 18512639 |
std::tr1::unordered_map | 77 | 772 | 8052 | 53094 | 658312 | 7429297 |
遍历,单位us | 100 | 1K | 10K | 100K | 1M | 10M |
std::map | 11 | 76 | 842 | 11603 | 155700 | 1771906 |
std::ext/hash_map | 47 | 430 | 4218 | 39880 | 470344 | 4781575 |
std::tr1::unordered_map | 1 | 1 | 2 | 1 | 2 | 1 |
查找,单位us | 100 | 1K | 10K | 100K | 1M | 10M |
std::map | 156 | 2111 | 30456 | 258709 | 4100260 | 59064394 |
std::ext/hash_map | 77 | 774 | 8056 | 56974 | 660231 | 7705527 |
std::tr1::unordered_map | 77 | 772 | 8051 | 54456 | 659537 | 7600263 |
删除,单位us | 100 | 1K | 10K | 100K | 1M | 10M |
std::map | 291 | 3641 | 49584 | 472414 | 6675897 | 92491113 |
std::ext/hash_map | 89 | 869 | 9068 | 86524 | 964767 | 10372650 |
std::tr1::unordered_map | 49 | 480 | 4879 | 33087 | 395098 | 4369617 |
结论:
1. std::tr1::unordered_map 与 std::ext/hash_map
任何情况下,如果要在这两个容器之间选择的话,我们毫不犹豫应该选择 unordered_map。因为他的性能在上述4中操作中均优于 hash_map,甚至可以说远远优于 hash_map。
2. std::tr1::unordered_map 与 std::map
map的性能总体来说是最差的。但是,当我们需要一个有序的关联容器的时候,我们必须选择std::map,因为 unordered_map 内部元素不是有序的,这一点从名字都可以看出来。除此之外都应该选择 unordered_map 。
3. 上述测试中,unordered_map 的遍历性能几乎是常数级别的,与常识不太相符,需要再研究研究。
附录:贴上源代码
说明:与测试程序稍有区别,这里的源码里没有MD5相关的代码以确保其他人能比较方便的直接拿去编译运行。
如有错误还请跟帖指出,非常感谢。
- #include <iostream>
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#include <string>
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#include <sstream>
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#include <list>
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#include <map>
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#include <sys/time.h>
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#include <ext/hash_map>
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#include <tr1/unordered_map>
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namespace zl
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{ //{{{
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struct equal_to
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{
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bool operator()(const char* s1, const char* s2) const
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{
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return strcmp(s1, s2) == 0;
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}
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};
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struct hash_string
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: public std::unary_function<std::string, std::size_t>
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{
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std::size_t
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operator()(const std::string& __s) const
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#ifdef __linux__
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{ return std::tr1::Fnv_hash<>::hash(__s.data(), __s.length()); }
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#else
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{ return std::tr1::_Fnv_hash<>::hash(__s.data(), __s.length()); }
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#endif
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};
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-
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struct hash_charptr
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: public std::unary_function<const char*, std::size_t>
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{
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std::size_t
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operator()(const char* __s) const
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#ifdef __linux__
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{ return std::tr1::Fnv_hash<>::hash(__s, strlen(__s)); }
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#else
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{ return std::tr1::_Fnv_hash<>::hash(__s, strlen(__s)); }
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#endif
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};
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}//}}}
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typedef std::list<std::string> string_list;
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typedef std::map<std::string, int> string_map;
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typedef __gnu_cxx::hash_map<std::string, int, zl::hash_string> string_hash_map;
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typedef std::tr1::unordered_map<std::string, int> string_unordered_map;
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void fill_list(string_list& slist, size_t count);
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uint64_t current_usec();
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int main( int argc, char* argv[] )
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{
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if (argc != 2 && argc != 3)
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{
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fprintf(stderr, "Usage:%s test_count rehash\n", argv[0]);
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fprintf(stderr, "For example:%s 10000 rehash\n", argv[0]);
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return -1;
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}
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size_t count = atoi(argv[1]);
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bool rehash = false;
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if (argc == 3)
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{
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rehash = true;
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}
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string_map smap;
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string_hash_map shash_map;
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string_unordered_map sunordered_map;
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if (rehash)
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{
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sunordered_map.rehash(count);
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}
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string_list slist;
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fill_list(slist, count);
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uint64_t start = 0;
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uint64_t end = 0;
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uint64_t map_insert_us = 0;
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uint64_t hash_map_insert_us = 0;
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uint64_t unordered_map_insert_us = 0;
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uint64_t map_traverse_us = 0;
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uint64_t hash_map_traverse_us = 0;
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uint64_t unordered_map_traverse_us = 0;
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uint64_t map_find_us = 0;
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uint64_t hash_map_find_us = 0;
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uint64_t unordered_map_find_us = 0;
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uint64_t map_delete_us = 0;
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uint64_t hash_map_delete_us = 0;
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uint64_t unordered_map_delete_us = 0;
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-
-
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// Insert test
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{//{{{
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string_list::iterator it(slist.begin());
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string_list::iterator ite(slist.end());
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//map insert
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start = current_usec();
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for (int i = 0; it != ite; ++it, ++i)
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{
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smap[*it] = i;
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}
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end = current_usec();
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map_insert_us = end - start;
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//hash_map insert
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it = slist.begin();
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start = current_usec();
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for (int i = 0; it != ite; ++it, ++i)
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{
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shash_map[*it] = i;
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}
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end = current_usec();
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hash_map_insert_us = end - start;
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//unordered_map insert
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it = slist.begin();
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start = current_usec();
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for (int i = 0; it != ite; ++it, ++i)
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{
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shash_map[*it] = i;
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}
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end = current_usec();
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unordered_map_insert_us = end - start;
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}//}}}
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// Traverse test
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{//{{{
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//map traverse
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{
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string_map::iterator it(smap.begin());
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string_map::iterator ite(smap.end());
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start = current_usec();
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for (int i = 0; it != ite; ++it)
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{
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i++;
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}
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end = current_usec();
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map_traverse_us = end - start;
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}
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//hash_map traverse
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{
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string_hash_map::iterator it(shash_map.begin());
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string_hash_map::iterator ite(shash_map.end());
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start = current_usec();
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for (int i = 0; it != ite; ++it)
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{
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i++;
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}
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end = current_usec();
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hash_map_traverse_us = end - start;
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}
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//unordered_map traverse
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{
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string_unordered_map::iterator it(sunordered_map.begin());
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string_unordered_map::iterator ite(sunordered_map.end());
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start = current_usec();
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for (int i = 0; it != ite; ++it)
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{
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i++;
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}
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end = current_usec();
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unordered_map_traverse_us = end - start;
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}
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}//}}}
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// Find test
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{//{{{
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string_list::iterator it(slist.begin());
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string_list::iterator ite(slist.end());
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//map find
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start = current_usec();
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for (int i = 0; it != ite; ++it, ++i)
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{
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smap[*it] = i;
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}
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end = current_usec();
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map_find_us = end - start;
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//hash_map find
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it = slist.begin();
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start = current_usec();
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for (int i = 0; it != ite; ++it, ++i)
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{
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shash_map[*it] = i;
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}
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end = current_usec();
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hash_map_find_us = end - start;
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//unordered_map find
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it = slist.begin();
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start = current_usec();
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for (int i = 0; it != ite; ++it, ++i)
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{
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shash_map[*it] = i;
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}
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end = current_usec();
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unordered_map_find_us = end - start;
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}//}}}
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// Delete test
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{//{{{
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string_list::iterator it(slist.begin());
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string_list::iterator ite(slist.end());
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//map delete
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start = current_usec();
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for (int i = 0; it != ite; ++it, ++i)
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{
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smap.erase(*it);
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}
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end = current_usec();
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map_delete_us = end - start;
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//hash_map delete
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it = slist.begin();
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start = current_usec();
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for (int i = 0; it != ite; ++it, ++i)
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{
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shash_map.erase(*it);
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}
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end = current_usec();
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hash_map_delete_us = end - start;
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//unordered_map delete
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it = slist.begin();
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start = current_usec();
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for (int i = 0; it != ite; ++it, ++i)
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{
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shash_map.erase(*it);
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}
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end = current_usec();
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unordered_map_delete_us = end - start;
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}//}}}
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//stat output
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std::cout << " insert, count " << count << std::endl;
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std::cout << " std::map " << map_insert_us << " us\n";
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std::cout << " std::ext/hash_map " << hash_map_insert_us << " us\n";
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std::cout << "std::tr1::unordered_map " << unordered_map_insert_us << " us\n";
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std::cout << "\n";
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std::cout << " traverse, count " << count << std::endl;
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std::cout << " std::map " << map_traverse_us << " us\n";
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std::cout << " std::ext/hash_map " << hash_map_traverse_us << " us\n";
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std::cout << "std::tr1::unordered_map " << unordered_map_traverse_us << " us\n";
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std::cout << "\n";
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std::cout << " find, count " << count << std::endl;
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std::cout << " std::map " << map_find_us << " us\n";
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std::cout << " std::ext/hash_map " << hash_map_find_us << " us\n";
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std::cout << "std::tr1::unordered_map " << unordered_map_find_us << " us\n";
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std::cout << "\n";
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std::cout << " delete, count " << count << std::endl;
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std::cout << " std::map " << map_delete_us << " us\n";
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std::cout << " std::ext/hash_map " << hash_map_delete_us << " us\n";
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std::cout << "std::tr1::unordered_map " << unordered_map_delete_us << " us\n";
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-
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return 0;
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}
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void fill_list(string_list& slist, size_t count)
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{
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for (size_t i = 0; i < count; ++i)
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{
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std::ostringstream oss;
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oss << i;
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//slist.push_back(MD5::getHexMD5(oss.str().c_str(), oss.str().length()));
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slist.push_back(oss.str());
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}
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}
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-
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uint64_t current_usec()
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{
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struct timeval tv;
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gettimeofday( &tv, NULL );
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return tv.tv_sec * 1000 * 1000 + tv.tv_usec;
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}
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