A data structure for optimistic concurrency control on ranges of bitwise-lexicographically-ordered keys.

Intended as an alternative to FoundationDB's skip list.

Hardware for all benchmarks is an AMD Ryzen 9 7900 with (2x32GB) 5600MT/s CL28-34-34-89 1.35V RAM

Microbenchmark

Skip list

ns/op	op/s	err%	ins/op	cyc/op	IPC	bra/op	miss%	total	benchmark
172.03	5,812,791.77	0.4%	3,130.62	879.00	3.562	509.23	0.0%	0.01	point reads
167.44	5,972,130.71	0.2%	3,065.14	862.27	3.555	494.30	0.0%	0.01	prefix reads
238.77	4,188,130.84	0.9%	3,589.93	1,259.30	2.851	637.12	0.0%	0.01	range reads
424.01	2,358,426.70	0.2%	5,620.05	2,242.35	2.506	854.80	1.7%	0.01	point writes
418.45	2,389,780.56	0.4%	5,525.07	2,211.05	2.499	831.71	1.7%	0.01	prefix writes
254.87	3,923,568.88	2.6%	3,187.01	1,366.50	2.332	529.11	2.7%	0.02	range writes
675.96	1,479,374.50	3.3%	7,735.41	3,468.60	2.230	1,386.02	1.8%	0.01	monotonic increasing point writes
137,986.20	7,247.10	0.6%	789,752.33	699,462.00	1.129	144,824.14	0.0%	0.01	worst case for radix tree
21.63	46,231,564.03	1.0%	448.00	107.14	4.181	84.00	0.0%	0.01	create and destroy

Radix tree (this implementation)

ns/op	op/s	err%	ins/op	cyc/op	IPC	bra/op	miss%	total	benchmark
12.42	80,500,398.66	0.8%	180.38	61.57	2.930	41.51	0.4%	0.01	point reads
15.17	65,917,580.99	0.2%	279.47	74.95	3.729	55.54	0.3%	0.01	prefix reads
38.16	26,202,393.91	0.1%	803.07	189.13	4.246	141.68	0.2%	0.01	range reads
20.20	49,504,615.44	0.4%	363.00	100.35	3.617	49.81	0.3%	0.01	point writes
41.99	23,816,559.99	0.3%	799.27	209.63	3.813	154.32	0.1%	0.01	prefix writes
46.28	21,607,605.88	1.5%	953.79	231.47	4.121	168.34	0.0%	0.01	range writes
80.99	12,347,449.98	0.9%	1,501.97	406.50	3.695	281.89	0.1%	0.01	monotonic increasing point writes
318,010.00	3,144.56	1.0%	3,994,511.50	1,657,831.50	2.409	805,969.50	0.0%	0.01	worst case for radix tree
75.85	13,183,612.56	0.5%	1,590.01	385.64	4.123	258.00	0.0%	0.01	create and destroy

"Real data" test

Point queries only, best of three runs. Gc ratio is the ratio of time spent doing garbage collection to time spent adding writes or doing garbage collection. Lower is better.

skip list

Check: 4.47891 seconds, 364.05 MB/s, Add: 4.55599 seconds, 123.058 MB/s, Gc ratio: 37.1145%

radix tree

Check: 0.963721 seconds, 1691.93 MB/s, Add: 1.3288 seconds, 421.924 MB/s, Gc ratio: 42.8819%

hash table

(The hash table implementation doesn't work on range queries, and its purpose is to provide an idea of how fast point queries can be)

Check: 0.804094 seconds, 2027.81 MB/s, Add: 0.652952 seconds, 858.645 MB/s, Gc ratio: 35.3885%