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The GIL exists because threads are a pain and it is still the simplest and fastest lock to ensure only one method accesses an attribute. poor algorithms hurt moreĪlso Python can have threads. Why do you think that you can give such a guarantee? There are of course various ways to attack NP complete problems, but none can be guaranteed to succeed within a reasonable time if the problem has a moderate size. Threading comes with worlds of pain: sync, locking (yes threading comes with locking that you would need to manage, something the GIL makes transparent from you.)ĭependency resolution is known to be NP complete. Some people, when confronted with a problem, think "I know, I'll use regular expressions." Now they have two problems. You can fork processes in python, you can use the threading.thread module & then you can use the multiprocess module (3.5 onwards) but then that doesn't answer why multithreaded/process would improve things? the old regex adage is true to threading: There is then cython which converts python to C so you have the benefit of python to write and the speed of CĪlso Python can have threads. Yes python is "slow" but it doesn't have to be (''.join() compared to str1+str2). Paludis is written in C++ and portage beats it (plenty of benchmarks on this). However, I think it is important to first ensure the validity of our approach with tests, comments, and suggestions that I didn't think of,Īnd once the basis is solid, make it as efficient as possible. There are numerous ways in which we can improve the speed of our prototype. This is where our solver can be quicker, as it does not iterate over all possible solutions but solves the constraints, guaranteeing an answer in limited time (few minutes). Moreover, python has a global lock which forbids the usage of threads (which could be very useful for emerge).Įmerge explores all the possible installations to find a solution, and this can take a very long time (it can also fail, which thus takes even more time). Python, even if it is quite quick, will never be as quick as C. emerge already partially solves these problem by using egencache files when possible (it is not always the case), and by being implemented asynchronously (that way, the solving is done at the same time as loading). ebuild file can take time, and loading 40,000 of them even more. In the portage tree, there are more or less 40,000 packages, each described in one bash script that can inherit from several. I see three reasons why emerge can be take a very long time:
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I agree with you that emerge could be quicker. To be honest when I read the subject of this thread, I thought you had implemented *faster* dependency calculations, because that’s the big problem of emerge IMO!īut otherwise if your system can be made faster than emerge, it would be great :).īut otherwise if your system can be made faster than emerge, it would be great. Of course, this solver can be improved in many ways, and comments, tests, and suggestions will be welcome and very useful. If a package is installable, our solver will find a solution, and if it is not, it can tell why (with an ugly syntax, sorry). Our new dependency solver is slower than the one of emerge and has far fewer functionalities (it is a prototype), but never fails: For instance, trying to install gnome-base/gnome only following emerge's advices (without looking at the documentation ) will only clutter the e file.
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Indeed, in some cases, emerge might not find a solution to an installation problem and give bad advice on how to continue. This prototype is implemented in python 2.7 and available here: Įmerge is an amazing tool, highly optimized and all, but has one default: it can (rarely) fail. I am very happy to announce that few colleagues and I implemented the prototype of a new dependency solver for emerge Posted: Sat 7:25 pm Post subject: Alternative dependency solver for Portage (a prototype) Gentoo Forums :: View topic - Alternative dependency solver for Portage (a prototype)Īlternative dependency solver for Portage (a prototype)