[theora-dev] GSoC - Theora multithread decoder

Ralph Giles giles at xiph.org
Fri Aug 15 00:21:53 PDT 2008

On 14-Aug-08, at 5:49 PM, Leonardo de Paula Rosa Piga wrote:

> This email is to inform what I have been doing since the mid-term.

Thanks, it's great to hear a report. A few comments/questions below.

> As I said before I did a pipelined implementation of these functions:
> (c_dec_dc_unpredict_mcu_plane + oc_dec_frags_recon_mcu_plane) and
> (oc_state_loop_filter_frag_rows + oc_state_borders_fill_rows) as
> explained in my previous email.
> But the results were not good. They were equal the implementation  
> without pipeline.

That's too bad. Do you have any hope that explicit threading would do  

> http://lampiao.lsc.ic.unicamp.br/~piga/gsoc_2008/comparison.png

Why are the error bars so large on three points on this plot? There  
data doesn't distinguish anything in that mcu range.

> My project is with few code, I tried to do my best. When I proposed  
> this project I knew that it would be very difficult. It was  
> challenging and I have learned a lot, specially  about the OpenMP  
> library.

You shouldn't be so discouraged. We were all aware this was a  
difficult proposal, but actually trying things is still useful work.

You should also commit all the code for these tests. That way others  
can reproduce and build on your work. One advantage of open source  
code repositories is that you can publish negative results. Google  
also wants all your code at the end of the program, and it's easier  
if they can pull it from our repository.


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