reporting speed
tree -- bitmap -- hash -- reservoirsampling -- reservoirsamplingC
16384			2.03		1.05		2.31		0.00504		0.00605		0.00596
8192			9.14		7.9		7.85		0.011		0.0121		0.0119
4096			8.15		13.3		7.73		0.0219		0.0241		0.0238
2048			7.96		20.8		7.59		0.0437		0.0481		0.0475
1024			7.47		27.6		7.49		0.0872		0.0957		0.0948
512			7.05		37.5		7.11		0.173		0.189		0.189
256			6.58		46.7		7.51		0.342		0.371		0.369
128			4.47		52.8		6.65		0.67		0.712		0.741
64			4.58		67.3		6		1.29		1.33		1.46
32			4.08		78.4		5.56		2.4		2.34		2.84
16			3.57		91.8		5.23		4.26		3.79		5.5
8			3.07		93		4.78		6.99		5.62		10.7
4			2.12		85.1		4.02		10.5		7.78		23.2
2			1.28		64.1		2.83		14.1		10.9		68.9
