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Re: [Pan-devel] article rescoring during download

From: Heinrich Müller
Subject: Re: [Pan-devel] article rescoring during download
Date: Sat, 22 Dec 2012 11:15:04 +0100
User-agent: Mozilla/5.0 (X11; Linux i686; rv:17.0) Gecko/17.0 Thunderbird/17.0

Am 22.12.2012 06:54, schrieb address@hidden:
Hi all,

I was curious what the latest pan looked like so I pulled down debian
unstable (0.139-1).  There was a remarkable slowdown and much higher CPU
usage when pulling binaries from large groups as compared to 0.133.

I grabbed the latest git code and did a little profiling.  Eventually I
found a curious call being made in pan/gui/, line 2527:

HeaderPane :: on_cache_added (const Quark& message_id)
   quarks_t q;
   _data.rescore_articles ( _group, q );    // here is slow
   rebuild_article_action (message_id);

That rescore_articles call eventually gets down to a std::set_intersection
over what I believe to be the entire list of articles in the group of

This on_cache_added call is made fairly often, possibly each time an
article's contents are retrieved.

I couldn't see anything terribly valuable in this call since I don't use
scoring other than to plonk authors so I commented out the three related
lines and saw my bandwidth get fully utilized again.

As for treating this, the code is doing an intersection with a single
element set (the one quark), which is effectively a find.  There might be a
faster find if these articles are already hashed.  I don't know enough
about the system to suggest a complete new codepath.  There might be a
"user doesn't use scoring" flag that flat avoids this call.

                                   Eric Ortega

Pan-devel mailing list
Thanks for noticing this bug, I'll fix it.


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