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
12.88	77,653,350.77	0.5%	185.37	64.45	2.876	41.51	0.4%	0.01	point reads
14.67	68,179,354.49	0.1%	271.44	73.40	3.698	53.70	0.3%	0.01	prefix reads
34.84	28,701,444.36	0.3%	715.74	175.27	4.084	127.30	0.2%	0.01	range reads
17.12	58,422,988.28	0.2%	314.30	86.11	3.650	39.82	0.4%	0.01	point writes
31.42	31,830,804.65	0.1%	591.06	158.07	3.739	82.67	0.2%	0.01	prefix writes
37.37	26,759,432.70	2.2%	681.98	188.95	3.609	96.10	0.1%	0.01	range writes
76.72	13,035,140.63	2.3%	1,421.28	387.17	3.671	257.76	0.1%	0.01	monotonic increasing point writes
297,452.00	3,361.89	0.9%	3,508,083.00	1,500,834.67	2.337	727,525.33	0.1%	0.01	worst case for radix tree
87.70	11,402,490.60	1.0%	1,795.00	442.09	4.060	297.00	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: 0.953012 seconds, 1710.94 MB/s, Add: 1.30025 seconds, 431.188 MB/s, Gc ratio: 43.9816%, Peak idle memory: 2.28375e+06

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%