There is still a couple of things that worries me. Given that they were 
mostly three working on Klein and that they never achieve a level of 
performance similar to their C++ implementation, I feel that the problem 
of boostrapping a system efficiently (in terms of development time) to 
achieve both simplicity and performance is not completely understood and 
therefore risky.

What I get from the paper, is that tools for inspecting and debugging 
the VM are of paramount importance but can be really tricky to get 
right.  That's something we should take into account in planning the 
work ahead.  At this point, I find it really hard to assess the amount 
of work in front of us.

I can't completely nail it yet, but there is something that makes 
meta-circular implementation of live systems a lot harder to think about 
than plain layered systems with different "languages" for each of the 
layers.

To be successful, I think we will have to learn as much as we can from 
other projects.  Talking about tools, I think the Maxine VM inspector is 
really interesting.

http://wikis.sun.com/display/MaxineVM/Inspector

Still interesting to note that Sun lost interest in the Klein project 
but still kept the idea of meta-cicularity...

Erick

Le 29/04/10 19:30 , Marc Feeley a écrit :
> Nice find Erick.  Well what can I say... the reasons they mention for Klein being metacircular are pretty much what I was saying for Tachyon.
>
> Marc
>
>
> On 2010-04-29, at 5:16 PM, Erick Lavoie wrote:
>
>    
>> "In constructing Klein, we have attempted to adhere to various principles, including object-orientation, metacircularity, heavy code reuse, reactiveness, and mirror-based reflection. We expect these principles to yield many benefits, including:
>> 	• A simpler, more malleable VM (because it is written almost entirely in a high-level language).
>> 	• Less replicated code (because the VM and the applications running on top of it are written in the same language and can share code, as can the VM and its development environment).
>> 	• Better performance (because the VM will be able to do optimizations across the entire code base, including the VM code itself - imagine being able to inline the hotspots of the VM right up into an application).
>> 	• Faster turnaround when making changes to the VM (because the VM will no longer be tied to C++ and its compilation system)."
>> http://kleinvm.sourceforge.net/
>>
>> However, the current version is not complete yet as a lot of things are yet to be done.
>>
>> Erick
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>>      
>
>