New implementation of LinkedHashSet/LinkedHashMap

[joshlemer]

Recently, @szeiger rewrote the implementations of mutable.HashMap and mutable.HashSet here. So far as I see there's no reason not to implement LinkedHashSet/Maps the same way, and in fact doing so will allow LinkedHashMaps/Sets to participate in hashcode sharing between:

• s.c.i.HashMap
• s.c.i.HashSet
• s.c.i.VectorMap
• s.c.m.HashMap
• s.c.m.HashSet
• s.c.m.HashMap#keySet
• s.c.i.HashMap#keySet
• s.c.i.VectorMap#keySet

as started here

[joshlemer]

@szeiger would you approve this?

[szeiger]

I haven't paid much attention to LinkedHashMap so far. I think any performance improvement would be welcome, especially if we can share code again with the new HashMap implementation.

[mghildiy]

I would like to contribute here.

[joshlemer]

@mghildiy it's all yours if you want it 😄

[adriaanm]

Is this still under consideration for RC1?

[mghildiy]

I went through mutable.HashMap and found changes broadly as:

• mixesin trait mutable.AbstractMap

• Class level parameters added: initialCapacity: Int, loadFactor: Double

• Replaced HashTable field with Array named: private[this] var table = new ArrayNode[K, V]

• field 'contentSize' intoduced

• method 'size' overriden

• inline method 'computeHash' added

• inline method 'index' added

• inline metod 'findNode' added to find an entry for input key(k) in array 'table'

• API methods overriden: sizeHint, addAll, remove

• abstract iterator class HashMapIterator added

• private classes Node, DeserializationFactory added

• Modified methods: apply, getOrElse, getOrElseUpdate, put

[szeiger]

"changes" is an understatement - it's a completely new implementation. I think the idea here is to start with a copy of the new HashMap implementation and make the required changes for keeping track of the links.

[joshlemer]

@mghildiy @szeiger is right, as well as for LinkedHashSet

[mghildiy]

Thanks for the inputs.

[pavelpavlov]

I would also like to contribute if there's need for it.
We use linked collections in our code very heavily.