[LLVMdev] [Polly]GSoC Proposal: Reducing LLVM-Polly Compiling overhead

Tobias Grosser tobias at grosser.es
Sat Mar 23 10:37:36 PDT 2013

On 03/23/2013 05:23 PM, tanmx_star wrote:
> Dear Tobies,
> Sorry for the late reply.
> I have checked the experiment and I found some of the data is mismatched because of incorrect manual copy and paste, so I have written a Shell script to automatically collect data. Newest data is listed in the attached file.

Yes, automatizing those experiments to make them reproducible is a very
good idea. I did not yet verify the numbers, but will as soon as your
script is online.

Two comments:

o Can you run also with the following flags:

D: -O3 -load LLVMPolly.so -mllvm -polly -mllvm -polly-optimizer=none
E: -O3 -load LLVMPolly.so -mllvm -polly -mllvm -polly-optimizer=none
   -mllvm -polly-code-generator=none

o Some numbers are again fishy:

adi: In your previous report you reported 0.953 seconds, the website now
     says 1.839 seconds.

ludcmp: In your previous report you reported 0.391 seconds, the website
        now says 1.346 seconds

instrument: It seems you rounded the previous numbers to one significant
            digit and calculated the performance difference from the
	    rounded numbers. I would prefer if you would use the
	    original numbers and you would only round when
	    displaying/printing the results

> Tobies, I have made a simple HTML page (attached polly-compiling-overhead.html) to show the experimental data and my plans for this project. I think a public webpage can be helpful for our further discussion. If possible, could you put it on Polly website (Either a public link or a temporary webpage) ?

Yes, I believe a website is a very good start to illustrate your
findings and to organize the information that you got. For now I propose
to host it yourself as I expect it to change often and you waiting for
me to add changes just adds overhead (there are plenty of free hosting
services). We can later move it to the Polly website.

Some comments on the content:

- Just put your name as the person who runs the project

I appreciate that you put my name on the top, but this is work you
started and that you will use as a summer of code project application.
So you should be the only person mentioned there

- Cite properly

Also, as this will later become an application, I believe it is
necessary to make clear what part of the document comes from you and
which part was something you got from reviews/external sources.
Specifically, if you copy a larger text from one of my emails, please
mark it accordingly.

- Typo


> I think I will try to remove unnecessary code transformations for canonicalization in next step.

Are you referring to the region simplification change, I was proposing
earlier? I believe this is a good change to work on as it is simple,
self contained and also a conceptual cleanup.

After this patch, I believe it is necessary to get more details about
your performance numbers to understand better where your work will be

All the best,

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