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.

$ clang++ --version

Ubuntu clang version 21.1.8 (6ubuntu1)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/lib/llvm-21/bin

Microbenchmark

Skip list

ns/op	op/s	err%	ins/op	cyc/op	IPC	bra/op	miss%	total	benchmark
171.37	5,835,467.28	0.5%	2,915.46	629.31	4.633	502.91	0.0%	0.01	point reads
168.16	5,946,774.62	0.5%	2,859.73	619.03	4.620	488.59	0.0%	0.01	prefix reads
245.86	4,067,294.63	0.3%	3,508.97	904.82	3.878	627.73	0.0%	0.01	range reads
381.14	2,623,691.76	0.2%	5,127.16	1,402.60	3.655	830.59	1.7%	0.01	point writes
376.24	2,657,887.07	0.3%	5,062.85	1,381.07	3.666	811.68	1.6%	0.01	prefix writes
257.09	3,889,688.44	3.8%	3,010.09	949.42	3.170	521.34	2.9%	0.01	range writes
629.71	1,588,026.28	4.0%	6,809.60	2,320.32	2.935	1,247.08	1.3%	0.01	monotonic increasing point writes
126,164.50	7,926.16	1.7%	772,460.25	463,264.67	1.667	141,512.00	0.2%	0.01	worst case for radix tree
15.33	65,217,669.23	0.4%	299.00	56.45	5.297	64.00	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
12.81	78,088,759.03	0.7%	187.38	47.15	3.974	33.70	0.5%	0.01	point reads
16.77	59,626,501.14	0.4%	277.61	61.74	4.497	44.76	0.4%	0.01	prefix reads
42.45	23,556,818.87	0.4%	856.96	156.09	5.490	126.22	0.2%	0.01	range reads
15.76	63,453,196.94	0.3%	249.89	58.04	4.306	33.21	0.5%	0.01	point writes
29.71	33,662,499.39	0.1%	509.14	109.33	4.657	70.26	0.5%	0.01	prefix writes
35.77	27,956,388.03	0.8%	614.18	131.72	4.663	85.57	0.1%	0.01	range writes
80.13	12,480,456.47	1.5%	1,279.04	294.90	4.337	234.68	0.1%	0.01	monotonic increasing point writes
360,748.00	2,772.02	2.6%	4,401,835.00	1,318,754.00	3.338	728,537.00	0.0%	0.01	worst case for radix tree
90.69	11,027,103.45	1.0%	1,686.00	333.80	5.051	284.00	0.0%	0.01	create and destroy

"Real data" test

Point queries only. 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: 4.42779 seconds, 368.253 MB/s, Add: 4.64942 seconds, 120.586 MB/s, Gc ratio: 28.8784%, Peak idle memory: 5.51735e+06

radix tree

Check: 0.891163 seconds, 1829.69 MB/s, Add: 1.23064 seconds, 455.579 MB/s, Gc ratio: 42.9417%, Peak idle memory: 2.28333e+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: 0.858484 seconds, 1899.33 MB/s, Add: 0.632886 seconds, 885.868 MB/s, Gc ratio: 41.252%, Peak idle memory: 0