[poppler] Migrating poppler to liblcms2 from liblcms1

Albert Astals Cid aacid at kde.org
Thu Jan 26 10:43:13 PST 2012

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 

> 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?


> 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
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