Make a Node a factory for itself

[jvassev]

How about this: make the node class a factory for itself :) (details in the commit message)

Zero reflection on the fast path + 90KB classes less.

It is not how a real gentleman would structure their Java code but the circumstances are extreme :)

[ben-manes]

I guess the only flaw is that this adds extra instance fields due to the factory node's unused ones? The alternatives would all have to add some, too, of course.

[jvassev]

Not really, the factory is stateless. Take the generated WSo for example:

    ...
   // factory methods:
    public <K2, V2> Node<K2, V2> newNode(K2 key, ReferenceQueue<K2> keyReferenceQueue, V2 value,
        ReferenceQueue<V2> valueReferenceQueue, int weight, long now) {
      return new WSo<>(key, keyReferenceQueue, value, valueReferenceQueue, weight, now);
    }

    public <K2, V2> Node<K2, V2> newNode(Object keyReference, V2 value,
        ReferenceQueue<V2> valueReferenceQueue, int weight, long now) {
      return new WSo<>(keyReference, value, valueReferenceQueue, weight, now);
    }

    public <K2> Object newLookupKey(K2 key) {
      return new LookupKeyReference<K2>(key);
    }

    public <K2> Object newReferenceKey(K2 key, ReferenceQueue<K2> referenceQueue) {
      return new WeakKeyReference<K2>(key, referenceQueue);
    }
...

There are no instance fields in the factory as it is now an interface.

[ben-manes]

There are no instance fields in the factory as it is now an interface.

Sure there is. WSo has a key and value field.

[jvassev]

Yes, the Wso used as factory will have some extra fields, but the Wso instances used as Node will have 4 more methods - no extra fields.

[ben-manes]

Yep, that's all I meant. It wasn't meant as more than an observation

[jvassev]

Sorry, I thought you are concerned with bloating the Node footprint :)

[jvassev]

Btw the K2, V2 are there to fix a few warnings. If we can live with the shadowing warnings that's 2K more saved and the psychological barrier of 700KB is passed :)

[ben-manes]

That would be okay or you could make NodeFactory typed. Then no shadowing would occur.

I'm not excited at the extra top-level fields, but I am also trying to see if there is any justification for that feeling. Its probably the right tradeoff.

[ben-manes]

When looking at the method handle approach, I guess it actually is worse because each MethodHandle holds a bunch of metadata fields. That prototype is at 680kb, with more work needed, but in comparison I think yours is nicer.

[jvassev]

The enum constants would also create 144 field + 144 classes (in the metaspace) when probably 2-3 are really used. I would expect that memory usage is reduced a bit - assuming an app has a few caches now it would also need a create a few nodeFactories. The enum approach would always create 144 factories.

[ben-manes]

Oh I am definitely for removing the enum. It was just easy to write when trying to get the codegen working. There was a lot of upfront development costs to get this project going.

I can merge this unless you are still iterating on any of it?

[ben-manes]

I typed the NodeFactory and its now at 700kb. Thanks! :)