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

[stephane ducasse]

On Dec 4, 2010, at 2:21 AM, Andreas Raab 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].
> 


But I'm not wrong your solution still requires to have one instance var to keep the id of the compiled methods saved on disc (so you cannot avoid to have the methodMap) with integer the integer itself encodes this information. No need for a map no need for an object.

> 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.
> 
> 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 :-)
> 
> Cheers,
>  - Andreas