利用unordered_map代替hash_map
- 实验环境
- 操作系统 fedora9
- 编译器版本 gcc4.3
- 实验方式
各种map使用插入和查找，比较速度和相关性能
- 代码
- 参考代码
- 下面测试说明了速度之间的比较：
| map类型 | 插入速度 | 插入和查找速度 |
|---|---|---|
| hashmap | 0m0.123s | 0m0.369s |
| map | 0m0.190s | 0m0.681s |
| unordered_map | 0m0.123s | 0m0.315s |
- 为什么要使用unordered_map代替hash_map？
- 因为标准化的推进，unordered_map原来属于boost分支和std::tr1中，而hash_map属于非标准容器。
- 另外，使用之后，感觉速度和hash_map差不多，但是支持string做key，也可以使用复杂的对象作为key。
- gxx需要添加编译选项：-std=gnu++0x或者-std=c++0x
- 在/usr/include/c++/4.3.0/backward/backward_warning.h文件中，明确写道：
This file includes at least one deprecated or antiquated header which may be removed without further notice at a future date. Please use a non-deprecated interface with equivalent functionality instead. For a listing of replacement headers and interfaces, consult the file backward_warning.h. To disable this warning use -Wno-deprecated.
/* A list of valid replacements is as follows:Use: Instead of:
<sstream>, basic_stringbuf <strstream>, strstreambuf
<sstream>, basic_istringstream <strstream>, istrstream
<sstream>, basic_ostringstream <strstream>, ostrstream
<sstream>, basic_stringstream <strstream>, strstream
<unordered_set>, unordered_set <ext/hash_set>, hash_set
<unordered_set>, unordered_multiset <ext/hash_set>, hash_multiset
<unordered_map>, unordered_map <ext/hash_set>, hash_map
<unordered_map>, unordered_multimap <ext/hash_set>, hash_multimap
<functional>, bind <functional>, binder1st
<functional>, bind <functional>, binder2nd
<functional>, bind <functional>, bind1st
<functional>, bind <functional>, bind2nd
<memory>, unique_ptr <memory>, auto_ptr