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Date: Tue, 15 Jan 2008 10:37:56 +0800
From: "Simon Chow" <simon.harmony@gmail.com>
To: dev@harmony.apache.org
Subject: Re: [drlvm][jitrino]A question of pipeline and method filter
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On 10 Jan 2008 17:59:47 +0300, Egor Pasko <egor.pasko@gmail.com> wrote:
>
> On the 0x3C7 day of Apache Harmony Simon Chow wrote:
> > On 18 Dec 2007 14:04:17 +0300, Egor Pasko <egor.pasko@gmail.com> wrote:
> > >
> > > On the 0x3AF day of Apache Harmony Simon Chow wrote:
> > > > Is there any analysis tools automatically choosing optimization path
> for
> > > my
> > > > source code.
> > > > If no,
> > > > Do you think such a tool can help developers a lot for archiving
> better
> > > > performance on Harmony.
> > > > I am trying to do some research for OPT, expecting for your advice.
> > > Thanks!
> > >
> > > Simon,
> > >
> > > I just want to add some of my long thoughts.. :)
> > >
> > > JITs aim at solving the problem of optimizing code with more or less
> > > universal approaches. We have this great tool as compilation pipeline
> > > management for developers' ability to experiment. JIT is already
> > > overly complicated with many pipeline phases influencing each other
> > > sometimes in very unexpected ways :)
> > >
> > > I do not believe in just-in-time meta-optimization because even the
> > > optimization tool (without meta) is already very complicated. However,
> > > if a user is ready to pay a lot if time to get a real bang in
> > > performance (of a single method or the whole app), they should
> > > consider searching in the big space of JIT configurations
> > > automatically, where some not very intelligent artificial intelligence
> > > might be promising here.
> >
> >
> > Sorry for a late reply.
> > Thank you for sharing so much thoughts! :)
> >
> > I have rethinked this question recently.
> > I strongly agree that it hard to write a program with such intelligence.
> > And I am curious about intelligent artificial intelligence you said :)
> What
> > is the method of searching configuration space?
>
> that's a big subject of machine learning. There are a bunch of methods
> with lots of modifications: Support Vector Machine (SVM), genetic
> algorithms, neural networks, boosting, etc. There is a wikipedia link
> collecting them:
>
> http://en.wikipedia.org/wiki/Machine_learning
>
> wanna dive into this nightmare? :)
>
> > Despiting the untested passes, Is there any possibility changing the
> > pipeline configuration (or create a new pipeline) for a particular set
> of
> > method which may archive better performance with some optimization pass
> by
> > analyzing profiling information?
>
> Do you want to implement a function that takes profile as parameter
> and tells which optpass to use?


Yes :)

Currently such tricks in Execution Manager are not supported, you can
> only set optimization passes based on method names (or parts of method
> names, for example, we construct different path for "...::<clinit>"
> methods that run only once")
>
> And I doubt one can write a sane function that tells which pass to use
> based on profile (and maybe bytecode supplemented).


Why is it? In my view, Hotspot uses profile to find 'hot section' and direct
its recompilation at runtime. I think this is similar to 'change pass based
on profile', isn't it?

Thanks!


So, I probably
> misunderstood you.
>
> > Thanks
> >
> > I suggest to apply artificial intelligence here because anyway we
> > > won't be able to understand what configurations are best using our own
> > > brains and hence we won't be able to write code for that.
> > >
> > > But be prepared to see that:
> > >
> > > a) not many of possible JIT pipelines make sense in terms of both
> > > compile-time and run-time performance plus memory footprint
> > >
> > > b) very little number of configurations would work in a stable way
> > > (because we do not test them, and some optimization passes are
> > > documented to work only in specific conditions, i.e. other
> > > optimizations preceded)
> > >
> > > What do you think?
> > >
> > > > On 17/12/2007, Mikhail Fursov <mike.fursov@gmail.com> wrote:
> > > > >
> > > > > On Dec 17, 2007 4:06 PM, Simon Chow <simon.harmony@gmail.com>
> wrote:
> > > > >
> > > > > > Thank you very much!
> > > > > >
> > > > > > So users should choose pipeline for methods before execution,
> isn't
> > > it?
> > > > >
> > > > > Yes.
> > > > >
> > > > >
> > > > > > Then I wants to know how to build a pipeline with the most
> efficient
> > > > > > compilation result of a specified method. Does it rely on the
> > > > > developer's
> > > > > > experience?
> > > > > >
> > > > > > Yes, it depends on developer's experience and on optimizations
> you
> > > > > expect
> > > > > to work for your method. E.g. if you know that your hot-spot
> method
> > > > > benefits
> > > > > from particular optimization - you just add it to the optimization
> > > path
> > > > > and
> > > > > tune it to do the best job for your method.
> > > > >
> > > > > --
> > > > > Mikhail Fursov
> > > > >
> > > >
> > > >
> > > >
> > > > --
> > > > From : Simon.Chow@Software School of Fudan University
> > >
> > > --
> > > Egor Pasko
> > >
> > >
> >
> >
> > --
> > From : Simon.Chow@Software School of Fudan University
>
> --
> Egor Pasko
>
>


-- 
>From : Simon.Chow@Software School of Fudan University

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