[MAGEEC] LLVM Talk Draft Proposal

[Simon Hollis]

Hi,

I think that the story that Simon is telling in that abstract is really
well explained and would certainly grab my attention and make me want to
see the talk :)

I do agree with James that we might want to be careful about how general we
make the 2x claim. In your abstact you are careful to say there are some
'examples' of this, but the natural question arises about the generality of
this improvement. It would be good to include some average improvement
figures in the talk to ward this problem off, even if the abstract remains
unchanged.

Simon


On 29 August 2014 10:30, James Pallister <James.Pallister at bristol.ac.uk>
wrote:

>  Hi Simon,
>
>
> We will present the latest performance results, which show
> that optimizing for energy is a double win, because such programs are
> almost
> always much faster, and will include examples where energy usage is halved
> and
> speed doubled compared to -O3.
>
> Do we know if MAGEEC can find these sets of optimizations? I can see a few
> complaints with saying we can double speed (assuming that this is coming
> from the genetic algorithm stuff I did a while ago). It was actually a
> genetic algorithm, made heavy use of optimization ordering and it was with
> an 'old' version of LLVM (3.1 or 3.2). Also it was on a Cortex-A8, rather
> than the embedded platforms we're targeting.
>
> It might be better to say that we've found cases where the potential is
> almost 3 times better than -O3, and we expect MAGEEC to get closer to that?
>
> I've attached the graph.
>
> Cheers,
> James
>
>
> On 27/08/14 08:26, Simon Cook wrote:
>
>   Hi all,
>
>  Jeremy and I have been working on an abstract for a talk at the upcoming
> LLVM conference. Here is what we have so far.
>
> "Title: Machine Guided Compilation and Compiling to Minimize Energy Usage
>
> Compilers currently optimize for execution time and code size. But in a
> world
> of diminishing battery life, ever larger data centers and nanoscale energy
> scavenging devices, what if the compiler could instead optimize for energy
> efficiency of the compiled code? Imagine having "-Oe" as an option to LLVM.
>
> Since June 2013 Embecosm and the University of Bristol, supported by the UK
> Technology Strategy Board have developed the Machine Guided Energy
> Efficient
> Compliation system. MAGEEC (www.mageec.org) uses machine learning to
> train a
> compiler on the combinations of compiler optimizations which will minimize
> the
> energy consumed by the compiled program. The original target of the
> project was
> to reduce the energy of compiled code by 40% compared to optimized code
> today.
>
> Unlike previous projects, MAGEEC is completely generic, capable of working
> with
> any compiler and target. It can optimize for any criterion, not just energy
> efficiency as we have used, and can be integrated with any machine learning
> approach. The project is entirely free and open source, with the code and
> all
> project design materials freely available online.
>
> In July 2014, the first complete version of the MAGEEC infrastructure was
> released, supporting both GCC and LLVM, and is now undergoing refinement
> and
> evaluation.  To support energy efficiency optimization, the project has
> developed its own low-cost (approx $50) energy measurement board, capable
> of
> sampling voltage and current up to 6 million times per second to an
> accuracy of
> better than 1%.  Training also requires a large pool of benchmark
> programs, and
> as part of this project we have also developed a new standard free and open
> source benchmark suite, BEEBS (www.beebs.eu), suitable for use with low
> energy
> deeply embedded systems.
>
> In this talk we will explain the detailed design of MAGEEC, comparing the
> challenges in developing for LLVM and GCC.  This will include the details
> of
> the integration with the machine learning system, allowing it to control
> the
> pass manager, and which allows us to select the best optimizations on a per
> function basis.  We will present the latest performance results, which show
> that optimizing for energy is a double win, because such programs are
> almost
> always much faster, and will include examples where energy usage is halved
> and
> speed doubled compared to -O3.
>
> We will conclude with a demonstration of MAGEEC in action on ARM
> processors,
> using the energy measurement board to measure the energy savings achieved."
>
>
> We're attempting to cover the entire history of the work we've done so
> far, as we don't have the benefit of having done a couple of talks
> previously for background information. If anyone has any thoughts before we
> submit this, that would be great. In particular, James, the graphs you had
> a few months ago with data from trying different passes with opt, have we
> quoted have the correct decrease in energy/execution time?
>
>  Many thanks,
> Simon
>
>
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