Re: Advanced concurrancy
Hi, I've been on the research pursuit regarding these subjects and I wonder why Erlang doesn't fit well into this category of concurrency. Also, from what I have seen, there hasn't been a recent interest in an updated interface. Maybe I'm mistaken and Erlang's features don't apply well. Thanks for your comments. Peter -- http://mail.python.org/mailman/listinfo/python-list
Re: Advanced concurrancy
on 04.08.2005 11:15 Matt Hammond said the following: Hi Stefan, It seems as though all components basically have to do busy waiting now. You are right - components are, for the most part, busy-waiting. Which is not a good thing! So do you plan on including a kind of scheduler-aware blocking communication (like the `channels` of the `tasklets` in stackless)? [snip] There is basic support for components to block, by calling the self.pause() method. From the next yield, this blocks further execution until data arrives on any inbox. [snip] ah, i was searching for blocking on a specific inbox, but this is actually a saner approach i think. why should you block on one inbox and ignore data coming in on another... There are quite probably better mechanisms around - hence the distinction, in the code, between microprocesses and components. We'd be very interested if yourself or other people want to play with alternative communication blocking mechanisms. i think in-out channels is probably the best way for easy to manage comunicating processes. I'd hope that even if the components and postboxes model doesn't work out in the long run, the underlying generator based microprocesses code could still be of some value to others! yes both levels will (it will take some time before i can use it here...), i think of it as a more complete version of some of the stackless features in standard python. (thanks again by the way) the magic.greenlets have 'cooperative microprocesses', but lack the more pipe-like communication facilities and the independency of the generators+scheduler based approach. the coroutine support in future pythons (see the generator PEPs) will probably make this easier... maybe:: next_inbox_to_read = yield blockon(inbox1, inbox2) this communication infrastructure is definitely a Good Thing (TM), the same holds for a standard environment or registry (wassitsname, your CAT thing) as you need at least one well-known point of reference in a 'distributed' system. dreamingmode now if someone could only cut the gordian knot of the GlobalInterpreterLock to make all this really concurrent... and then, when she's at it, allow transparent distribution of components in a network... ;-) /dreamingmode -- http://mail.python.org/mailman/listinfo/python-list
Re: Advanced concurrancy
on 04.08.2005 00:36 Michael Sparks said the following: Peter Tillotson wrote: I'm quite interested in the mini version and also using the modules as mobile code rather than installing it formally. I'll document it slightly better and post up on the website in the next 48 hours or so. In the meantime, the optimisation test which includes a slightly modified mini-axon can be found here: http://cvs.sourceforge.net/viewcvs.py/kamaelia/Sketches/OptimisationTest/ Specifically the file simplegame.py. Hi, sorry to intrude here. I looked at Kamaelia (Axon actually) recently and I liked it, what I did miss in the code (maybe I just did not find it) is a blocking way for send-ing and recv-ing from in/outboxes that the scheduler is aware of. It seems as though all components basically have to do busy waiting now. So do you plan on including a kind of scheduler-aware blocking communication (like the `channels` of the `tasklets` in stackless)? (as you have a postman already - not a bad idea i think if you compare with multi-agent-systems theory (see jade) - it could be responsible for alerting the scheduler of box.has_data) Cheers, Stefan -- http://mail.python.org/mailman/listinfo/python-list
Re: Advanced concurrancy
Hi Stefan, It seems as though all components basically have to do busy waiting now. You are right - components are, for the most part, busy-waiting. Which is not a good thing! So do you plan on including a kind of scheduler-aware blocking communication (like the `channels` of the `tasklets` in stackless)? (as you have a postman already - not a bad idea i think if you compare with multi-agent-systems theory (see jade) - it could be responsible for alerting the scheduler of box.has_data) There is basic support for components to block, by calling the self.pause() method. From the next yield, this blocks further execution until data arrives on any inbox. The un-pausing action is actually performed by code within the component itself, though this is in effect, as you suggested it might be, instigated by the postman microprocess. A simple example would be an improved 'consoleEcho' component: class consoleEchoer(Axon.Component.component): def main(self): while 1: yield 1 while self.dataReady(inbox): print self.recv(inbox) self.pause() That said, if you look at the code, you'll see that probably the majority of components do not make good use of this yet! There are quite probably better mechanisms around - hence the distinction, in the code, between microprocesses and components. We'd be very interested if yourself or other people want to play with alternative communication blocking mechanisms. I'd hope that even if the components and postboxes model doesn't work out in the long run, the underlying generator based microprocesses code could still be of some value to others! regards Matt -- http://mail.python.org/mailman/listinfo/python-list
Re: Advanced concurrancy
Peter Tillotson wrote: I've not yet had a chance to try some examples, but i've looked through the documentation. It feels quite familiar, It hopefully should. The approach is based essentially on an asynchronous hardware approach, on the recognition that the fundamental reason that hangs together is because it can be reasoned about in a similar manner to CSP. (That naturally leads to similarities of course with Occam) but i'd say that it is closer to Jade, the fipa (federation of intelligent physical agents) compliant agent framework Thanks - I've not come across those - I'll have to take a look at that in detail. (With a cursory look, they sounds similar to an application area a colleague is interested in investigating) than CSP or pi calculus. I like the behaviour (component microthread) model, but the advantage of CSP / pi calculus is that the resulting distributed system remains open to mathematical analysis. Indeed. However, by trying to have the same basic limitations in the system, Kamaelia should be amenable to the sort of approaches taken by hardware verification systems. It's possibly worth mentioning that there is one person at BBC RD who is extremely interested in applying CSP style analysis techniques to Kamaelia systems whom I sure would be interested in chatting to you. (Indeed the similarities between Kamaelia and CSP is biggest reason for his interest :-) The idea of a verification system for software that is actually in use for real world systems would be extremely nice/useful to have (though not simple to achieve). FWIW, I am interested in hearing suggestions on changing the system to make it more amenable to mathematical analysis. (Largely because I'm a fan of formal methods where possible, but pragmatically view TDD as the current most practical way of getting towards the levels of reliabiliy aimed for by formal methods) For concurency its is the best framework i've seen :-) Thanks! Have you come across the pylinda tuplespace implementation. It might be well worth a look. I have, and I liked what I saw :) I might be barking up the wrong tree - but it seems to me that there could be considerable overlap between tuplespaces and mailboxes, Probably the closer match is the co-ordinating assistant tracker (I can see what you mean though). That provides a basic global key/value store/retrieve service, which in a concurrent system is probably most akin to a Linda tuplespace. In a biological system it's more akin to the hormonal system which is more of the model I like to think of as to /when/ to use that part of the system. (Evolution having more 'experience' than me on how to build a massively concurrent system after all !!) It's generally only used at present for one of two purposes: * Finding services that already exist (so that we don't try to open two displays for example) * Stats collection. Using a Linda tuplespace there would be an interesting next move, however we generally only extend the system based on specific need rather than exploring architecture (Which I'm sure you understand!). though you did mention that you were moving towards twisted as the underlying platform for the future. Perhaps not underlying, but definitely interoperating with (It seems rather wasteful to reinvent wheels). I'm quite interested in the mini version and also using the modules as mobile code rather than installing it formally. I'll document it slightly better and post up on the website in the next 48 hours or so. In the meantime, the optimisation test which includes a slightly modified mini-axon can be found here: http://cvs.sourceforge.net/viewcvs.py/kamaelia/Sketches/OptimisationTest/ Specifically the file simplegame.py. This includes a cutdown version of Axon that's about 100 lines long (lines 41 - 144 specifically), with the important classes being: class microprocess(object): class newComponent(object): class scheduler(microprocess): class component(microprocess): class send_one_component(component): def linkage(source,sink): I'll probably zip the Axon directory and distribute the zip with the code, adding the zip to the python path dynamically. Sounds interesting. If you go ahead with this we'd be interested in hearing how you get on. Best Regards, Michael. -- http://mail.python.org/mailman/listinfo/python-list
Re: Advanced concurrancy
I've not yet had a chance to try some examples, but i've looked through the documentation. It feels quite familiar, but i'd say that it is closer to Jade, the fipa (federation of intelligent physical agents) compliant agent framework than CSP or pi calculus. I like the behaviour (component microthread) model, but the advantage of CSP / pi calculus is that the resulting distributed system remains open to mathematical analysis. For concurency its is the best framework i've seen :-) Have you come across the pylinda tuplespace implementation. It might be well worth a look. I might be barking up the wrong tree - but it seems to me that there could be considerable overlap between tuplespaces and mailboxes, though you did mention that you were moving towards twisted as the underlying platform for the future. I'm quite interested in the mini version and also using the modules as mobile code rather than installing it formally. I'll probably zip the Axion directory and distribute the zip with the code, adding the zip to the python path dynamically. cheers p Michael Sparks wrote: Peter Tillotson wrote: Hi, I'm looking for an advanced concurrency module for python and don't seem to be able to find anything suitable. Does anyone know where I might find one? I know that there is CSP like functionality built into Stackless but i'd like students to be able to use a standard python build. Please take a look at Kamaelia* - it /probably/ has what you're after by the sounds of things. Currently the unit for sequential process can be either generators or threads, and is single CPU, single process, however we do expect to make the system multi-process and multi-system. * http://kamaelia.sourceforge.net/ Currently it runs on Linux, Mac OS X, Windows and a subset works nicely on Series 60 mobiles. (That has separate packaging) It works with standard Python versions 2.2 and upwards. The basic idea in Kamaelia is you have a class that represents a concurrent unit that communicates with local interfaces only which are essentially queues. The specific metaphor we use is that of an office worker with inboxes and outboxes with deliveries made between outboxes to inboxes. There also exists a simple environmental/service lookup facility which acts like an assistant in the above metaphor, and has natural similarities to a Linda type system. (The actual rationale for the assistant facility though is based on biological systems. We have communicating linked concurrent components - which is much like many biological systems. However in addition to that most biological systems also have a hormonal system - which is part of the thinking behind the assistant system) Generators (when embedded in a class) lend themselves very nicely to this sort of model in our experience /because/ they are limited to a single level (with regard to yield). It's probably suitable for your students because we've tested the system on pre-university trainees, and vacation trainees, and found they're able to pick up the system, learn the basic ideas within a week or so (I have some exercises on how to build a mini- version if that helps), and build interesting systems. For example we had a pre-university trainee start with us at the beginning of the year, learn python, Kamaelia, and build a simple streaming system taking a video file, taking snapshots and sending those to mobile phones and PC's - this was over a period of 3 months. He'd only done a little bit of access in the past, and a little bit of VB. Well that as well as a simple learning system simulating a digital TV decode chain, but taking a script instead of a transport stream. We recently made a 0.2.0 release of the system (not announced on c.l.p yet) that includes (basic) support for a wide range of multimedia/networked apps which might help people getting started. Some interesting new additions in the release are an IPython integration - allowing you to build Kamaelia systems on the fly using a shell, much like you can build unix pipelines, as well as a visual introspection tool (and network graph visualiser) which allows you to see inside systems as they are running. (This has turned out to be extremely useful - as you can expect with any CSP-type system) The specific use cases you mention are also very closed aligned with our aims for the project. We're essentially working on making concurrency easy and natural to use, (starting from the domain of networked multimedia). You can do incremental development and transformation in exactly the way it sounds like you want, and build interesting systems. We're also working on the assumption that if you do that you can get performance later by specific optimisations (eg more CPUs). * Example of incremental component development here: http://tinyurl.com/dp8n7 By the time we reach a 1.0 release (of Kamaelia) we're also aiming to be able to
Re: Advanced concurrancy
On 28 Jul 2005 10:41:54 -0700, [EMAIL PROTECTED] [EMAIL PROTECTED] wrote: Asynchrony is not concurrency. If you have to turn your code inside out, (that is, if you have to write your code such that the library calls your code, rather than vice versa) it's very much *not* concurrency: it's just asynchrony. While Twisted makes asynchronous code relatively easy to write and maintain, it's just not concurrency. I can't simply drop my single-threaded code into it and have it work, like I can with a truly concurrent system. Jeremy When you can ever just simply drop any single-threaded code into an enviroment where it is sharing the resources and data with other executing code simulataniously, it just have it work, that will be the day. Unfortunately, in practice, this simply is not how things work. For code to operate peacefully together, it must be designed to do so. Even when code is running in seperate processes, they must work together to share some resources, and that is simply the way of things. Concurrency can not (and perhaps should not) be an automatic fix-all pill. -- http://mail.python.org/mailman/listinfo/python-list
Re: Advanced concurrancy
Cheers Guys, I have come across twisted and used in async code. What i'm really looking for is something that provides concurrency based on CSP or pi calculus. Or something that looks much more like Java's JSR 166 which is now integrated in Tiger. Peter Tillotson wrote: Hi, I'm looking for an advanced concurrency module for python and don't seem to be able to find anything suitable. Does anyone know where I might find one? I know that there is CSP like functionality built into Stackless but i'd like students to be able to use a standard python build. I'm trying to develop distributed / Grid computing modules based on python. The aim is to be able to use barriers for synchronisation and channels for communication between processes running on a single box. Then the jump to multiple processes on multiple boxes and eventually to MPI implementations. Hopefully, each jump should not be that big a leap. Of course it would be nice if there was a robust way of managing concurrency in python aswell ;-) p -- http://mail.python.org/mailman/listinfo/python-list
Re: Advanced concurrancy
Peter Tillotson [EMAIL PROTECTED] writes: I have come across twisted and used in async code. What i'm really looking for is something that provides concurrency based on CSP or pi calculus. Or something that looks much more like Java's JSR 166 which is now integrated in Tiger. Python doesn't have anything that fancy. You could look at: pyro.sf.net - Python remote objects using sockets poshmodule.sf.net - objects shared between processes using shared memory Queue module - synchronized queues for interthread communications in one process It would be nice if there were something like Queue that used MPI. Underneath there could be either sockets, shared memory, some special multiprocessor interconnect, or whatever. -- http://mail.python.org/mailman/listinfo/python-list
Re: Advanced concurrancy
Peter Tillotson wrote: Hi, I'm looking for an advanced concurrency module for python and don't seem to be able to find anything suitable. Does anyone know where I might find one? I know that there is CSP like functionality built into Stackless but i'd like students to be able to use a standard python build. Please take a look at Kamaelia* - it /probably/ has what you're after by the sounds of things. Currently the unit for sequential process can be either generators or threads, and is single CPU, single process, however we do expect to make the system multi-process and multi-system. * http://kamaelia.sourceforge.net/ Currently it runs on Linux, Mac OS X, Windows and a subset works nicely on Series 60 mobiles. (That has separate packaging) It works with standard Python versions 2.2 and upwards. The basic idea in Kamaelia is you have a class that represents a concurrent unit that communicates with local interfaces only which are essentially queues. The specific metaphor we use is that of an office worker with inboxes and outboxes with deliveries made between outboxes to inboxes. There also exists a simple environmental/service lookup facility which acts like an assistant in the above metaphor, and has natural similarities to a Linda type system. (The actual rationale for the assistant facility though is based on biological systems. We have communicating linked concurrent components - which is much like many biological systems. However in addition to that most biological systems also have a hormonal system - which is part of the thinking behind the assistant system) Generators (when embedded in a class) lend themselves very nicely to this sort of model in our experience /because/ they are limited to a single level (with regard to yield). It's probably suitable for your students because we've tested the system on pre-university trainees, and vacation trainees, and found they're able to pick up the system, learn the basic ideas within a week or so (I have some exercises on how to build a mini- version if that helps), and build interesting systems. For example we had a pre-university trainee start with us at the beginning of the year, learn python, Kamaelia, and build a simple streaming system taking a video file, taking snapshots and sending those to mobile phones and PC's - this was over a period of 3 months. He'd only done a little bit of access in the past, and a little bit of VB. Well that as well as a simple learning system simulating a digital TV decode chain, but taking a script instead of a transport stream. We recently made a 0.2.0 release of the system (not announced on c.l.p yet) that includes (basic) support for a wide range of multimedia/networked apps which might help people getting started. Some interesting new additions in the release are an IPython integration - allowing you to build Kamaelia systems on the fly using a shell, much like you can build unix pipelines, as well as a visual introspection tool (and network graph visualiser) which allows you to see inside systems as they are running. (This has turned out to be extremely useful - as you can expect with any CSP-type system) The specific use cases you mention are also very closed aligned with our aims for the project. We're essentially working on making concurrency easy and natural to use, (starting from the domain of networked multimedia). You can do incremental development and transformation in exactly the way it sounds like you want, and build interesting systems. We're also working on the assumption that if you do that you can get performance later by specific optimisations (eg more CPUs). * Example of incremental component development here: http://tinyurl.com/dp8n7 By the time we reach a 1.0 release (of Kamaelia) we're also aiming to be able to integrate cleanly with Twisted (on Twisted's grounds), but it is highly usable already - especially in your area. (In CVS we have tools for building game type systems easily Tk integration as well. Tk based CSP systems are particularly fun to work with (as in fun, not fun :). One project we are seriously looking at is a visual editor for these CSP-type systems, since that appears now to be low hanging fruit. We've got a white paper about Kamaelia here: * http://www.bbc.co.uk/rd/pubs/whp/whp113.shtml This is textualisation of a presentation I gave at ACCU earlier in the year and is an overview of the core areas of the system - hopefully enough to let you know whether to look further! I also gave an updated talk at Europython - the presentation for which can be downloaded from here: * http://www.python-in-business.org/ep2005/talk.chtml?talk=2589track=692 Last week I also gave a more pragmatic, shorter talk at Open Tech which is an introduction to Kamaelia, it's goals, and several examples of CSP type systems ranging from simple audio clients/servers through to presentation tools. That presentation can be downloaded from here: *
Advanced concurrancy
Hi, I'm looking for an advanced concurrency module for python and don't seem to be able to find anything suitable. Does anyone know where I might find one? I know that there is CSP like functionality built into Stackless but i'd like students to be able to use a standard python build. I'm trying to develop distributed / Grid computing modules based on python. The aim is to be able to use barriers for synchronisation and channels for communication between processes running on a single box. Then the jump to multiple processes on multiple boxes and eventually to MPI implementations. Hopefully, each jump should not be that big a leap. Of course it would be nice if there was a robust way of managing concurrency in python aswell ;-) p -- http://mail.python.org/mailman/listinfo/python-list
Re: Advanced concurrancy
Twisted [1] includes lots of support for asyncronous concurrency, using deferreds. There is also the possiblity of PEP 342's [2] concurrency through enhanced generators, and being able to pass data to the generator every iteration. There are ways to simulate this, as well. I've written a recipe [3] for it over at ASPN. Personally, I like the generator approach better, because it gives a feel of threads, but with direct control of the timeslicing, a better sense of understanding, and doesn't rely on things happening in the background, like deferreds often do. On 7/28/05, Peter Tillotson [EMAIL PROTECTED] wrote: Hi, I'm looking for an advanced concurrency module for python and don't seem to be able to find anything suitable. Does anyone know where I might find one? I know that there is CSP like functionality built into Stackless but i'd like students to be able to use a standard python build. I'm trying to develop distributed / Grid computing modules based on python. The aim is to be able to use barriers for synchronisation and channels for communication between processes running on a single box. Then the jump to multiple processes on multiple boxes and eventually to MPI implementations. Hopefully, each jump should not be that big a leap. Of course it would be nice if there was a robust way of managing concurrency in python aswell ;-) p -- http://mail.python.org/mailman/listinfo/python-list -- http://mail.python.org/mailman/listinfo/python-list
Re: Advanced concurrancy
Asynchrony is not concurrency. If you have to turn your code inside out, (that is, if you have to write your code such that the library calls your code, rather than vice versa) it's very much *not* concurrency: it's just asynchrony. While Twisted makes asynchronous code relatively easy to write and maintain, it's just not concurrency. I can't simply drop my single-threaded code into it and have it work, like I can with a truly concurrent system. Jeremy -- http://mail.python.org/mailman/listinfo/python-list
Re: Advanced concurrancy
Peter Tillotson wrote: Hi, I'm looking for an advanced concurrency module for python and don't seem to be able to find anything suitable. Does anyone know where I might find one? I know that there is CSP like functionality built into Stackless but i'd like students to be able to use a standard python build. I'm trying to develop distributed / Grid computing modules based on python. The aim is to be able to use barriers for synchronisation and channels for communication between processes running on a single box. Then the jump to multiple processes on multiple boxes and eventually to MPI implementations. Hopefully, each jump should not be that big a leap. Of course it would be nice if there was a robust way of managing concurrency in python aswell ;-) And deferredGenerator in twisted.internet.defer is the robust way for that. It blows up python readability in contrast,but once you got them and made your library I think they are also usable. I do believe, without deferreds in the core ,python will have bad times surviving the net, but that's really an opinion. Have fun, Paolino -- http://mail.python.org/mailman/listinfo/python-list
