language-ext v3.2.0 Release Notes
Release Date: 2019-06-20 // almost 5 years ago-
🚀 Included in this release are performance improvements for
Option<A>
,OptionUnsafe<A>
, andSeq<A>
.Seq<A>
has now also become astruct
to stop the usage ofnull
but also to facilitate the new performance improvements.ISeq<A>
will eventually be deprecated and so there are now[Obsolete]
warnings - but I won't kill it for quite a long time, I just want to discourage its usage.🚀 I'm doing this as a
beta
release because the changes toSeq<A>
are enormous - well, a complete re-write. It is now entirely lock free and internally has three possible states:Lazy
,Strict
, andEmpty
- which allows for improved performance for the happy paths.🐎 I will keep language-ext in beta for a while as I go through the library optimising what I believe are the most used features. I am doing this now because I feel the library is settling down now - as in there's less churn of features and interfaces - and so now is a good time to start squeezing the most performance out of it.
🚧 Mostly this will involve trying to reduce memory allocations where possible as well as inlining operations that make unnecessary calls (which were there to keep everything super generic under the hood). This will make long term maintenance a bit harder, which is why it needed to wait until now.
🐎 Performance timings
🐎 Below are some tests I've used to tweak the performance, the timings are all relative from the old
Seq
to the new, so my machine's spec shouldn't matter.Streaming a lazy sequence
🐎 This performance test wraps a lazy enumerable in a
Seq
and then streams them in one-by-one via theforeach
loop and saves the value in aresults
array.var seq = Seq(Range(0, count));foreach(var item in seq) { results[j] = item; j++; }
Old Seq<A>
New Seq<A>
138 ns / op
54 ns / op
🐎 So a performance improvement of 2.55 times. Evaluating an
IEnumerable<T>
lazy sequence is about29 ns / op
which whilst faster thanSeq<A>
doesn't have the memoisation thatSeq
has. (or any of the other cool features, for that matter)Streaming a strict sequence
A lot of the time I find I'm working with strict sequences - i.e. non-lazy. This is the happy path for sequences and a lot of optimisations can happen if the code knows the sequence isn't lazy
var seq = Seq(Range(0, count));seq = seq.Strict();foreach (var item in seq) { results[j] = item; j++; }
Old Seq<A>
New Seq<A>
16.1 ns / op
10.9 ns / op
🐎 A performance improvement of ~32.3%. This isn't quite as significant as the lazy stream improvements, but interestingly this is now faster than
List<T>
from the BCL, which measures around12.5 ns / op
.➕ Adding an item to the end of a
Seq
Essentially calling this, many times:
seq = seq.Add(value);
Old Seq<A>
New Seq<A>
49.5 ns / op
33.2 ns / op
Around a 33% improvement. This isn't quite as fast as the
10.9 ns / op
of the BCL'sList<T>
, I will work on this some more. But this is an immutable, thread-safe, data structure - which the BCLList<T>
definitely isn't.➕ Adding an item to the beginning of a
Seq
Essentially calling this, many times:
seq = value.Cons(seq);
Old Seq<A>
New Seq<A>
40 ns / op
20 ns / op
🐎 Twice as fast. This isn't far off
List<T>.Add
- and so that's why I think I can makeSeq<A>.Add
gain a bit more speed. Note: the BCL'sList<T>.Insert(0, x)
which is the equivalent toSeq<A>.Cons
has terrible performance at10310 ns / op
. So that's one to look out for!Other
Seq<A>
functionsMost
Seq<A>
functions will either evaluate a lazy stream, a strict stream, orAdd
orCons
items. And so nearly allSeq<A>
related functionality will gain due to these changes.Option<A>
andOptionUnsafe<A>
🐎 I haven't done any performance timings for these types, as most improvements are to reduce unnecessary allocations. I have removed the support for lazy options - if anyone misses them then I'll probably create an
OptionLazy<A>
type. I'd rather not, but I felt that becauseOption<A>
is probably the most used type in lang-ext then it should always be on the happy path. This has reduced a lot of unnecessary branching and has allowed the internals ofOption<A>
andOptionUsafe<A>
to be simplified.Feedback please
⚡️ Because these are some big changes, if you have an app with lots of unit tests it'd be great if you could verify that they all still run with these updates. I have obviously made sure all of the existing unit tests pass and have built a number of test harnesses to check that everything still works and to verify the thread-safeness of
Seq
, but changes like these have a habit of kicking you when you least expect it. So, any help will be gratefully received.