[Bug 662777] Caps negotiation got a lot slow since the last release

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=662777
  GStreamer | gstreamer (core) | git

--- Comment #25 from Vincent Penquerc'h <vincent.penquerch at collabora.co.uk> 2011-11-07 14:26:32 UTC ---
(In reply to comment #19)
> (From update of attachment 200344 [details])
> Looks good but you still have the old commit message. This version now
> preserves the order. And it's not only useful for _intersect_first() but also
> for the other intersect() variant so add it there too.
> 
> Did you check if this really speeds up something? The caps are simpler but
> you're creating duplicates of the caps

It does not speed up anything on the test case I have here, as the caps are
already ordered in strict increasing generality order. The simplification
itself does slow down a little bit the whole operation (from 8.2 seconds to 8.4
seconds here, though timings have a fair bit of jitter), but since a full
simplification makes it less than a second, I expect that lesser simplification
would help in some cases.

I'd tried a nifty pre-sort and post-merge with bins based on structure name, to
reduce the N in O(N^2), but unfortunately this did not help, as the actual
looping is very fast compared to the few hits that take all the time, so the
number of costly ops is still the same :(

Up to you if you want to leave that patch out since I don't have an actual test
case where it helps.

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