[poppler] Migrating poppler to liblcms2 from liblcms1

[Albert Astals Cid]

El Dilluns, 23 de gener de 2012, a les 11:16:03, Maria, Marti va escriure:
> Hi,
> In my testings lcms2 is significantly faster that lcms1 except when using
> floating point, then lcms2 favors precision.

Is this precision is so important to justify a 10x slowliness? Maybe it'd be a 
good idea to have a fallback fast mode for those not willing to take that 10x 
hit?

> http://littlecms2.blogspot.com/2010/03/xput-comparative-119-vs-20.html
> 
> Altona test does many different color conversions it would be interesting to
> know which transformation is going slow.

Attached the callgrind output of running poppler there, you can see the time 
is almost totally spent on creating the transforms.

Wild guess: I'm wondering if the thing is that not transformations are all 
precalculated (meaning a faster overall if you do lots of access) and 
previously they were done each time and thus if we end up doing "few" 
transformations it was just much faster?

Cheers,
  Albert

> 
> Regards
> Marti
> 
> ________________________________________
> From: Till Kamppeter [till.kamppeter at gmail.com]
> Sent: Monday, January 23, 2012 8:58 AM
> To: Albert Astals Cid
> Cc: poppler at lists.freedesktop.org; Maria, Marti; Sebastien Bacher; Koji
> Otani Subject: Re: [poppler] Migrating poppler to liblcms2 from liblcms1
> On 01/22/2012 11:18 PM, Albert Astals Cid wrote:
> > Same thing, altona_technical_1v2_x3.pdf still goes up from x seconds to
> > 10x seconds when going from lcms1 to lcms2.
> > 
> > That is in my opinion not acceptable (of course i'm not ruling out that
> > we in poppler are using lcms2 wrong). Till, does your ubuntu work cover
> > fixing the regressions of moving from lcms1 to lcms2 or all your work
> > covers is making stuff compile?
> 
> I downloaded altona_technical_1v2_x3.pdf from
> http://www.eci.org/doku.php?id=es:downloads and tried pdftops on Ubuntu
> Oneiric (11.10, lcms1) and on Precise (12.04, lcms2, Koji Otani's patch)
> and with lcms1 it takes 3.5 seconds and with lcms2 17.5 seconds.
> 
> The same problem occurs with Ghostscript: There the same transition
> happened from Oneiric to Precise and here Oneiric is much faster with
> this file, too. In Precise PDF rendering for printing is done by
> Ghostscript and not by Poppler, so lcms2 is already used for printing in
> Precise for some time. As there are no performance complaints by users
> yet, it seems that for everyday files there is not such a significant
> performance loss. and this
> 
> Marti, can you check what is the problem with lcms2 and this PDF file
> and also why most files are somewhat slower with lcms2?
> 
>     Till
> _______________________________________________
> poppler mailing list
> poppler at lists.freedesktop.org
> http://lists.freedesktop.org/mailman/listinfo/poppler
-------------- next part --------------
A non-text attachment was scrubbed...
Name: callgrind.out.24674.zip
Type: application/zip
Size: 559725 bytes
Desc: not available
URL: <http://lists.freedesktop.org/archives/poppler/attachments/20120126/beccafe7/attachment-0001.zip>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: captura de pantalla1.png
Type: image/png
Size: 36272 bytes
Desc: not available
URL: <http://lists.freedesktop.org/archives/poppler/attachments/20120126/beccafe7/attachment-0001.png>