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
17.03	58,732,967.93	0.6%	276.28	87.96	3.141	52.15	0.4%	0.01	point reads
19.52	51,239,158.04	0.3%	367.16	101.50	3.617	61.92	0.3%	0.01	prefix reads
47.74	20,947,676.63	0.5%	998.16	247.43	4.034	161.64	0.2%	0.01	range reads
23.14	43,207,824.89	0.4%	408.18	121.64	3.356	70.20	0.3%	0.01	point writes
38.02	26,302,115.66	0.1%	709.72	199.70	3.554	134.26	0.3%	0.01	prefix writes
44.28	22,583,559.17	0.9%	825.19	233.10	3.540	141.48	0.2%	0.01	range writes
85.50	11,695,990.63	0.5%	1,488.16	455.68	3.266	289.22	0.1%	0.01	monotonic increasing point writes
338,388.50	2,955.18	3.3%	4,097,087.00	1,809,996.00	2.264	759,645.00	0.0%	0.01	worst case for radix tree
84.84	11,787,313.59	1.4%	1,716.02	440.50	3.896	271.00	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: 1.05813 seconds, 1540.97 MB/s, Add: 1.32071 seconds, 424.508 MB/s, Gc ratio: 42.2067%

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%