On 20 January 2016 at 16:36, phil@highoctane.be <phil@highoctane.be> wrote:
On Wed, Jan 20, 2016 at 4:19 PM, Peter H. Meadows via Pharo-dev <pharo-dev@lists.pharo.org> wrote:
---------- Forwarded message ---------- From: "Peter H. Meadows" <peter.h.meadows@googlemail.com> To: Pharo Development List <pharo-dev@lists.pharo.org> Cc: Date: Wed, 20 Jan 2016 15:17:59 +0000 Subject: Re: [Pharo-dev] [ANN] Pharo bootstrap Cool. Any chance someone can explain for beginners to understand what's going on here? Why is cleaning the image not as simple as running it and deleting any object that wasn't used?
The point is not to clean but to start with an empty object engine and fill it in with the minimum required core.
But why should this not end up with the same end result? One way is to start with nothing, and only add stuff we need to make it run/boot, and the other way is to start with what we have, and remove anything that is not needed to make it run/boot. In both cases don't you end up with the same thing?
Currently, the image is the result of an evolutionary process and rebuilding it from zero was not possible.
I wonder if they thought about this when they created the first image. Didn't they think 'hey, we should really have a way for anyone to create new images from nothing'? Or was it just that they didn't get around to making this tool?
This maes it possible to audit the whole build process, create different base image for various purposes (very small, headless with no UI objects at all, using the object engine in a completely different way that is used today).
That makes the image the result of a fully reproducible process, from a file of zero bytes, to a file with a working image.
That would make us master the whole chain. Today, there is still black magic in the image, due to the history.
That's an exciting development. For example, in C, one compiles all files, and links, giving the exe. All that from a file of zero size. We will be able to do the same kind of thing at the image level.
Also, this allows to experiment with new low level mechanisms. This is currently not possible since it makes us like performing surgery on our own brain. Also, the Oz-inspired system will help in exploring other image memories (small or large) and manipulate them as entities. At this point, this is also not common pratice.
HTH Phil, wishing to master the mitosis competency...
(Thanks in advance)
On 20 January 2016 at 12:52, Guillermo Polito <guillermopolito@gmail.com> wrote:
Well, there is no formal specification⦠But I could summarize the features as follows (and as Christophe points mostly out)
OzVM supports having two images in logically separated spaces. This separation is achieved by using the free bit in the object header. Thus we support only two spaces by now.
- The main addition is actually a new primitive: #resumeFromSpecialObjectsArray that receives an special objects array as argument and: - resumes the execution from the active process of such array - on context switch, if the VM is running from a second special objects array, it will return to the first one instead.
- fixes to primitives/bytecodes that assume a single special objects array. e.g., - #someObject and #nextObject should only iterate objects from the correct âspaceâ - #isNil comparisons should take the correct nil - the GC should set the correct nil object on Weak containers
The extensions I made are about 20 overrides to StackPrimitive and NewObjectMemory methods.
The rest is implemented completely on image side. We use mirror primitives to manipulate objects from other space (as each image/space has itâs own selector table).
I have in my long TODO list see if the "clever hackâ I did can be supported in a nice manner on top of Spurâs segmented memory. However, I should stop commencing new projects and start finishing them :P.
On 20 ene 2016, at 9:03 a.m., Christophe Demarey <Christophe.Demarey@inria.fr> wrote:
Hi Eliot,
Le 19 janv. 2016 à 19:29, Eliot Miranda a écrit :
Hi All,
great news! Where can I read a specification of the Oz VM facilities?
I do not know all the details of the Oz VM but basically, it is a standard stack interpreter vm specialized to be able to run 2 images at the same time on top of it. Guillermo made it possible by using one available bit in the object header of objects to mark the ownership of an object (e.g. is my object from image1 or image2?). Then, he mainly had to specialize VM primitives dealing with objects retrieval from memory. By example, he had to modify the garbage collector to set the right nil instance (yes, we have 2 images so 2 nil instances. we need to take the one of the active image) when an object is garbage collected; the primitive someObject has to return an object from the active image, etc. There is also a way to switch execution from an image to the other just by switching the special objects array reference.
You can find some information in: https://guillep.github.io/files/publications/Poli15Thesis.pdf. The Oz code is in http://smalltalkhub.com/#!/~Guille/ObjectSpace and in https://github.com/guillep/OzVM The current implementation uses Cog 6.6.1and OzVM-GuillermoPolito.22. I do not know if Guille has a more formal specification of the Oz VM.
If you have advices on what is the best way to handle two distinct object (memory) spaces in Spur, they will be welcomed :)
Cheers, Christophe
_,,,^..^,,,_ (phone)
On Jan 19, 2016, at 6:29 AM, Christophe Demarey <christophe.demarey@inria.fr> wrote:
Hi all,
In case you do not know, we work on bootstrapping Pharo, i.e. create a Pharo image from sources, not based on a previous image (well, we use a pharo image to produce it but no code / state from it).
This process will allow to define a minimal Pharo kernel (currently 52 packages but we could have it far smaller) and to modularize the whole image (currently packages have too much dependencies on packages already loaded into the image). The bootstrap process also allows to write down the recipe to initialize a new image from scratch (some code is missing in the image or is wrong). In addition, I think we will clean a lot of historical objects that are not used anymore.
With the amazing work done by Guillermo Polito during his Phd (around Espell, Oz): https://guillep.github.io/files/publications/Poli15Thesis.pdf, we succeeded to get a first prototype of a bootstraped Pharo 5 image (from 5.392). This prototype is able to run an eval command line handler and to log output / errors. Not all classes are yet initialized and you cannot yet save / restart this image but it is a big step forward. It is a 4 mb image (could be half the size without unicode data). You can download it at:
http://chercheurs.lille.inria.fr/~demarey/pmwiki/pub/pharo-bootstrap/pharo-b....
Next steps are to have a bootstrapped image fully working, then to load packages on top of it (like network, sunit) to produce a minimal image. Then, we need to implement an Oz VM on top of Spur. After that, we need to work on a reliable way to build the bootstrap (not too sensitive to changes in the image).
Christophe.
------- demarey@193-51-236-143:~/dev/rmod/bootstrap/bootstrap-2016-01-19$ ../pharo bootstrap.image --no-default-preferences eval "1 + 1" 2 demarey@193-51-236-143:~/dev/rmod/bootstrap/bootstrap-2016-01-19$ ../pharo bootstrap.image --no-default-preferences eval "'a' , 'b'" 'ab' demarey@193-51-236-143:~/dev/rmod/bootstrap/bootstrap-2016-01-19$ ../pharo bootstrap.image --no-default-preferences eval "1 / 0" ZeroDivide SmallInteger>>/ UndefinedObject>>DoIt OpalCompiler>>evaluate OpalCompiler(AbstractCompiler)>>evaluate: SmalltalkImage>>evaluate:
EvaluateCommandLineHandler>>no (source is Undeclared) no source in EvaluateCommandLineHandler>>evaluate: in Block: no source BlockClosure>>on:do: EvaluateCommandLineHandler>>evaluate: EvaluateCommandLineHandler>>evaluateArguments EvaluateCommandLineHandler>>activate EvaluateCommandLineHandler class(CommandLineHandler class)>>activateWith:
BasicCommandLineHandler>>no (source is Undeclared) no source in PharoCommandLineHandler(BasicCommandLineHandler)>>activateSubCommand: in Block: no source BlockClosure>>on:do: PharoCommandLineHandler(BasicCommandLineHandler)>>activateSubCommand: PharoCommandLineHandler(BasicCommandLineHandler)>>handleSubcommand PharoCommandLineHandler(BasicCommandLineHandler)>>handleArgument:
BasicCommandLineHandler>>no (source is Undeclared) no source in PharoCommandLineHandler(BasicCommandLineHandler)>>activate in Block: no source BlockClosure>>on:do: PharoCommandLineHandler(BasicCommandLineHandler)>>activate PharoCommandLineHandler>>activate PharoCommandLineHandler class(CommandLineHandler class)>>activateWith:
PharoCommandLineHandler class>>no (source is Undeclared) no source in PharoCommandLineHandler class>>activateWith: in Block: no source NonInteractiveUIManager(UIManager)>>defer: PharoCommandLineHandler class>>activateWith: no source in BasicCommandLineHandler>>activateSubCommand: in Block: no source BlockClosure>>on:do: BasicCommandLineHandler>>activateSubCommand: BasicCommandLineHandler>>handleSubcommand BasicCommandLineHandler>>handleArgument: no source in BasicCommandLineHandler>>activate in Block: no source
SmallInteger>>no (source is Undeclared)
UndefinedObject>>no (source is Undeclared)
AbstractCompiler>>no (source is Undeclared)
SmalltalkImage>>no (source is Undeclared)
BlockClosure>>no (source is Undeclared)
EvaluateCommandLineHandler>>no (source is Undeclared)
EvaluateCommandLineHandler>>no (source is Undeclared)
CommandLineHandler class>>no (source is Undeclared)
BasicCommandLineHandler>>no (source is Undeclared)
BasicCommandLineHandler>>no (source is Undeclared)
PharoCommandLineHandler>>no (source is Undeclared)
UIManager>>no (source is Undeclared)
UndefinedObject>>no (source is Undeclared)
CommandLineUIManager>>no (source is Undeclared)
SmalltalkImage>>no (source is Undeclared)
DelayMicrosecondScheduler>>no (source is Undeclared)
BlockClosure>>no (source is Undeclared)
SmalltalkImage>>no (source is Undeclared)
WeakArray class>>no (source is Undeclared)
ps: source cannot be displayed because there is no formatter available in the bootstrap