Dear Squeakers,
Meta:
I have some understanding and some practical problems.
I haven't worked for years at ParcPlace/Disney/Cincom and I haven't written an ST interpreter. Possibly some of these things would be a good foundation to go deeper here... ;-)
I don't think, I'm stupid in principle, but sometimes I get this feeling *here*...
Possibly I shouldn't go too deep into this stuff, because it is quiet special and needs deep insights to become productive here; but currently I'm interested in it and motivated to go a little deeper... And I think some of mine problems are resulting from a lack of existing or found documentation. BTW: It is natural, that in this special area there isn't so much doc as in more common areas: Not everybody is interested in looking into the mechanisms of compiling and VMs; and more less in improving this stuff...
Concrete:
Squeaks ST80 implementation of BlockContexts without any BlockClosures is far away from Eliot's paper. I think I need an understanding of BlockClosures first and have just searched for papers about BlockClosures, without success.
With platform dependent I've meaned the 'hybrid context' together with 'native frame' stuff, introduced to support just in time compilers. To use this we need a Jitter. Am I correct here?
I'm thinking (not working! (would be interesting, though)) about a less ambitious solution with the current 'normal' VM.
I have a non commercial VW:
sr@Klaus:~ > vw5i -version Copyright © 1999 Cincom Systems, Inc. All Rights Reserved. Release identification ... OE version: 51 platform: 168 release: 51.4 flags: 0 VI version: 0 minor: 0 release: 0 variant: 0 From version: 0 platform: 0 release: 0.1 flags: 0
; there is some documentation, but to get an understanding of 'classical' BlockClosures some kind of paper related to an earlier version of VW without so much optimizations would be better. Moreover I don't fully understand the VW-VM definition: E.g. when which temporary variables are pushed why onto the stack before calling a BC and how they are pop'ed thereafter. In short: the logic of compiling by the Compiler and interpreting the compiled result by the VM; especially in regard to BCs. Just looking with an inspector onto CompiledMethods and CompiledBlocks and jumping around from method to method isn't sufficient to get deeper insights.
Vassili Bykov wrote:
Stephan,
The only thing I can add to what Tim already said is you can read "Lisp in Small Pieces" or SICP.
Thanks for the hint; is this somewhere in the net?
Greetings,
Stephan
They explain in detail some things Eliot's paper assumes the reader knows. (Though I still can't see how it is not "platform independent"--unless you want a Smalltalk VM on a Turing machine or something).
--Vassili
-- Vassili Bykov VisualWorks development vassili@parcplace.com
-----Original Message----- From: Stephan Rudlof [mailto:sr@evolgo.de] Sent: Saturday, July 29, 2000 8:43 AM To: squeak@cs.uiuc.edu Subject: Re: Block closures
Vassili Bykov wrote:
Eliot's OOPSLA paper describes that improvement, as well as
gives a good
intro to closure implementation in VW in general:
http://www.squeak.org/oopsla99_vmworkshop/oopsla99-contexts.pdf
I have to put some water into the wine here... ;-(
The paper is interesting and stands in the tradition of and is related to earlier VW implementations, which have extended the ST80 specification. It addresses the realization of very fast block closures, so far so good.
But to reach this goal, native stack layout is used and different kind of mappings of ST contexts to native stack frames. I think this fits good into JIT-Compiler work, but
*** this isn't a platform independent approach ***.
Moreover I don't see a realization just by changing the interpreter and ST contexts, methods and related things.
To reach platform independence, we should use a slower, but compatible realization of block closures. More sophisticated techniques should be applied after a working common variant.
BTW: Are there any papers describing BlockClosures without referring to native stack layout?
Greetings,
Stephan
-- Vassili Bykov VisualWorks development vassili@parcplace.com
-----Original Message----- From: Tim Rowledge [mailto:tim@sumeru.stanford.edu] Sent: Thursday, July 27, 2000 2:29 PM To: squeak@cs.uiuc.edu Subject: Re: Block closures
Mats, if you're serious about this, do yourself a big favour and talk to Eliot Miranda about his recent (as in a year or so ago) improvements to block handling in VW; he's explained it to me but I
couldn't for the
life of me explain it to you and get it right. Basically I think it ... oh hell, get him to explain it.
And don't forget to talk with Ian Piumarta to make sure he isn't duplicating the work (he said at ECOOP he'd tackle it soon) and that you don't do anything that will break the jitter. Craig Latta did some pretty serious planning with Ian some time ago on this
subject so he
might some useful input for you as well. And don't forget the VM changes you'll need.
And don't forget to work out howto get there from here; the bit that has always put me off trying anything. I'd suggest using the SystemTracer to clone a new image with BlockClosures rather than trying
to manage with
both styles. At least with Squeak you can simulate the
new system and
have a decent debugger.
tim
-- Tim Rowledge, tim@sumeru.stanford.edu,
http://sumeru.stanford.edu/tim
To err is human; to forgive, beyond the scope of the Operating System.
-- Stephan Rudlof (sr@evolgo.de) "Genius doesn't work on an assembly line basis. You can't simply say, 'Today I will be brilliant.'" -- Kirk, "The Ultimate Computer", stardate 4731.3