Non blocking data structures for Go.

The List type is implemented using A Pragmatic Implementation of Non-Blocking Linked-Lists by Timothy L. Harris.

The Hash type is implemented using Split-Ordered Lists: Lock-Free Extensible Hash Tables by Ori Shalev and Nir Shavit with the List type used as backend.

On my laptop I created three different benchmarks for a) regular Go map types, b) Go map types protected by sync.RWMutex and c) the gotomic.Hash type.

The benchmarks for a) and b) can be found at https://github.com/zond/tools/blob/master/tools_test.go#L83 and the benchmark for c) at https://github.com/zond/gotomic/blob/master/hash_test.go#L116.

The TL;DR of it all is that the benchmark sets runtime.GOMAXPROCS to be runtime.NumCPU(), and starts that number of goroutines that just mutates and reads the tested mapping.

Last time I ran these tests I got the following results:

a)

BenchmarkNativeMap	 5000000	       567 ns/op

b)

BenchmarkMyMapConc	  200000	     10694 ns/op
BenchmarkMyMap	 1000000	      1427 ns/op

c)

BenchmarkHash      500000	      5146 ns/op
BenchmarkHashConc	  500000	     10599 ns/op

Conclusion: As expected a) is by far the fastest mapping, and it seems that the naive RWMutex wrapped native map b) is much faster at single thread operation, and about as efficient in multi thread operation, compared to c).

I find it likely that c) is more efficient than b) at higher levels of concurrency, but for regular uses an RWMutex wrapped map is probably a safer bet.

See https://github.com/zond/gotomic/blob/master/examples/example.go or https://github.com/zond/gotomic/blob/master/examples/profile.go

http://go.pkgdoc.org/github.com/zond/gotomic

No known bugs.

I have not tried it on more than my personal laptop however, so if you want to try and force it to misbehave on a heftier machine than a 4 cpu MacBook Air please do!

It would be nice to have a Hash#DeleteIfPresent that atomically deletes matching key/value pairs, but since the implementation is slightly harder than trivial and I see no immediate use case I have been too lazy. Tell me if you need it and I might feel motivated :)