Using lcms2 in Poppler or Ghostscript slows down rendering performance

[tillkamppeter]

For Ubuntu Precise (12.04) we want to migrate completely from the old liblcms1 to liblcms2, as the new library is maintained upstream:

https://bugs.launchpad.net/ubuntu/+source/lcms/+bug/885324

Unfortunately there is a regression in liblcm2. Most files get rendered slightly slower (5-10%) when Poppler is linked with liblcms2 instead of liblcms1 (for Ghostscript I have no test results).

But most important is that some files render significantly slower. An example is altona_technical_1v2_x3.pdf from http://www.eci.org/doku.php?id=es:downloads. Simply run it through "pdftops" (convert to PostScript with Poppler) or "gs" (screen-display with Ghostscript) on Ubuntu Onneiric (11.10, using liblcms1) and Ubuntu Precise (12.04, using liblcms2) and you see that the rendering is between 5 and 10 times slower with liblcms2. See also comments #16, #37 and #38 on

https://bugs.launchpad.net/ubuntu/+source/lcms/+bug/885324

and

http://www.mail-archive.com/poppler@lists.freedesktop.org/msg06258.html

[mstimberg]

I ran pdftops altona_technical_1v2_x3.pdf through valgrind. The problem seems to be that cmsStageSampleCLut16 in cmslut.c ends up calling XFormSampler16 (cmsopt.c) 10 million times which eventually leads to 30 million calls of DefaultEvalParametricFunction (cmsgamma.c). The calculations call the math library's pow function 60 million times in total which seems to be where most of the time is spent.

[thomas-weber]

Is this issue still relevant? I tried to reproduce the number of calls in mstimberg's comment, but I'm unable to do so with lcms2 2.8. There, DefaultEvalParametricFunction is called 29053 times.

[mm2]

Historical issue that finally I can close :-)
just use the fast float plug-in, included in lcms2-2.10