unoreder_map 内部实现

http://www.cppblog.com/Chipset/archive/2012/08/26/188340.html

双数组哈希unordered_xxx

简单的类层次结构

以静态表unorered_set为例，工作原理见下图

简单的效率测试

Sample是本处讲述的双数组unordered_xxx，standard是编译器的unordered_xxx，boost1.50表示它的unordered_xxx

测试环境：

Win7 x64 Ultimate (Kernel 6.1.7601), g++4.6.3 64bit (-O3), Intel Xeon E31230 3.2GHz, Hynix DDR3-1333 ECC DIMM 4GBx2 Dual Chanel, P8B-X (Intel Cougar Point C202), WD5000AADS-00M2B0, AMI BIOS 12/26/2011, Sapphire Radeon HD 5750 GDDR5 1GB, Samsung SyncMaster BX2250(H) (Digital) 1920x1080@60Hz

测试结果：

静态表		unordered_map (64位随机数1百万个)			unordered_multimap(32位随机数1百万个)			unordered_set(字符窜253674个单个窜长200以上)			unordered_multiset(字符窜81536个单个窜长低于20)
		Sample	standard	boost1.50	Sample	standard	boost1.50	Sample	standard	boost1.50	Sample	standard	boost1.50
插入	ms	67.8525	180.929	212.671	50.9687	150.95	199.598	85.0928	73.3596	142.383	27.8756	18.9638	16.4688
查找		72.4412	62.884	93.388	48.6442	51.0842	87.3587	68.6096	63.8798	145.687	21.9548	10.7675	12.969
删除		168.938	179.079	289.612	126.764	164.087	285.196	135.997	66.9415	136.711	53.0243	12.6135	9.6811
内存	MB	32	40	52	24	36	52	81.2	85	85.1	9.3	9.9	10.6

动态表		unordered_map (64位随机数1百万个)			unordered_multimap(32位随机数1百万个)			unordered_set(字符窜253674个单个窜长200以上)			unordered_multiset(字符窜81536个单个窜长低于20)
		Sample	standard	boost1.50	Sample	standard	boost1.50	Sample	standard	boost1.50	Sample	standard	boost1.50
插入	ms	129.523	270.424	262.842	92.9128	256.856	291.372	143.654	127.587	149.45	38.2729	26.3448	18.4614
查找		70.2685	61.971	94.4114	46.1028	51.017	85.9693	75.2463	66.1863	149.023	22.7871	11.7799	14.482
删除		148.089	178.864	295.409	110.26	163.184	297.173	133.305	70.1459	145.462	42.8773	13.0186	10.0248
内存	MB	32.2	40	52	24.2	36	52	82.7	85.1	85	7.8	9.5	9.6

 

Visual Studio 2012编译运行结果：

静态表		unordered_map (64位随机数1百万个)		unordered_multimap(32位随机数1百万个)		unordered_set(字符窜253674个单个窜长200以上)		unordered_multiset(字符窜81536个单个窜长低于20)
		Sample	standard	Sample	standard	Sample	standard	Sample	standard
插入	ms	59.999	188.476	50.9861	174.008	142.694	146.148	27.3501	20.3516
查找		48.1513	78.2629	33.3826	55.69	80.589	136.024	19.8892	16.9792
删除		163.05	215.432	121.721	199.238	205.691	204.848	40.771	13.3655
内存	MB	32	60.7	24	45.4	96.5	111	5.7	10.8

动态表		unordered_map (64位随机数1百万个)		unordered_multimap(32位随机数1百万个)		unordered_set(字符窜253674个单个窜长200以上)		unordered_multiset(字符窜81536个单个窜长低于20)
		Sample	standard	Sample	standard	Sample	standard	Sample	standard
插入	ms	118.021	273.997	91.9337	252.155	249.369	243.164	41.6276	24.7281
查找		45.8492	78.085	33.4889	58.0067	92.2518	138.624	21.8552	16.6643
删除		144.097	217.688	103.813	201.557	192.211	209.361	30.966	13.7178
内存	MB	32.5	60.7	24.7	45.4	97.6	111	5.7	8.8

编译：

尽管尽可能使用C++98的语法，但编译Sample的unordered_***代码仍然需要比较新的编译器(老编译器无能为力)，例如g++4.6.3以后版本，VC++2012等。

Source Code: http://www.cppblog.com/Files/Chipset/double_array.7z