[Vm-dev] Re: SmallInetger as methods was not ready yet....now maybe?

Mariano Martinez Peck marianopeck at gmail.com
Mon Dec 6 09:19:05 UTC 2010

On Sat, Dec 4, 2010 at 2:21 AM, Andreas Raab <andreas.raab at gmx.de> wrote:

> On 12/3/2010 4:18 PM, Eliot Miranda wrote:
>> BTW, Mariano's use of SmallIntegers rather than wrappers is an attempt
>> to get a very compact image and seems a reasonable experiment.  Using
>> wrappers would defeat his use-as-little-memory-as-possible purpose.
> Not at all. The design of objects-as-methods was deliberately done such
> that one could use a single wrapper for multiple methods. The only thing you
> need is to map from selector to method being executed. For example:
> MethodSwapper>>run: aSelector with: argsArray in: aReceiver
>        "Execute the given method"
>        method:= methodMap at: aSelector.
>        ^aReceiver withArgs: argsArray executeMethod: method
> Then you install a single MethodSwapper instance like here:
> swapper := MethodSwapper new.
> Morph selectorsAndMethodsDo:[:sel :meth| swapper methodMap at: sel put:
> meth].
> Morph selectorsDo:[:sel| Morph addSelector: sel withMethod: swapper].
> At this point the only overhead you have is what's in the (single)
> MethodSwapper instance and even with a most naive implementation (looking up
> the index by selector) you'd have 8 bytes per method in your image which I
> suspect is well below 5% of the image size.

But that's exactly what I want to avoid. I can even create the proxy class
compact, and I would have 4 bytes if I serach by equality the compiledMethod
in all classes.

> And then of course you can start *really* looking at getting the size down.
> Did you know that Dan once did a very neat hack where he replaced all
> symbols with integers? Works great and if you do that you not only reclaim
> the space for the symbols but also don't need a lookup at all :-)
Yes, I know that. I even saw that the VM was "prepare" to support
SmallIntegers as key in the MethodDict. However, I have 2 questions for that

- Is that transparent for the develope?   I mean, are we still able to do
things like   MyClass >> #foo  ?  or we are force to do  MyClass methodDict
at: 42 ?

- To get those symbols garbageCollected, I guess I need to compact the
symbol table all the time.


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