# Page by page compilation time

I am trying to locate the bottlenecks in compilation for a very large document.

The accepted answer to this Question addresses the problem in a neat way but the method only works for pdflatex (and not for LuaTeX and XeTeX) because the \pdfelapsedtime primitive is only available in pdflatex.

However this Question creates a \pdfelapsedtime analogue for LuaTex.

The question is how to do in XeTeX

Since XeTeX does not have timekeeping capabilities, the shell escape feature is left. The disadvantage is the large overhead of running external programs with duration variations.

The following example runs with plain and LaTeX formats. It is written for Perl under Linux and requires the -shell-escape switch:

xetex -shell-escape test
xelatex -shell-escape test


The interface is (macros names are prefixed with xetk):

• \xetkresettimer is similar to \pdfresettimer the timer is reset.

• \xetksetelapsedtime gets the current time difference to the last call of \xetkresettimer.

• \xetkelapsedtime contains the time in seconds as decimal number, set by \xetksetelapsedtime.

File test.tex:

\catcode\@=11 % \makeatletter

\def\xetk@resetargs{}

\def\xetkresettimer{%
\begingroup
% the end of line character must be disabled,
% otherwise it could add active characters, ...
\endlinechar=-1 %
\openin\xetk@pipe="|perl -e '%
use Time::HiRes qw[gettimeofday];%
@t=gettimeofday;%
print qq[@t]%
'"\relax
\closein\xetk@pipe
\endgroup
}
\xetkresettimer
\wlog{XeTeX timekeeping initialization: \xetk@resetargs}
\def\xetkelapsedtime{0}

\edef\xetksetelapsedtime{%
\begingroup
\endlinechar=-1 %
\openin\xetk@pipe="|perl -e '%
use Time::HiRes qw[tv_interval];%
print tv_interval(\string\@ARGV)%
' -- \noexpand\xetk@resetargs"\relax
\closein\xetk@pipe
\endgroup
}

%%% Testing

\def\test{%
\xetkresettimer
\xetksetelapsedtime
\immediate\write16{* Elapsed time: \xetkelapsedtime\space s}%
}

\test
\test
\test
\test
\test

\csname @@end\endcsname\end % end job


Macro \test resets the timer (external program is called), does nothing and calls again the external program to get the time difference:

* Elapsed time: 0.032371 s
* Elapsed time: 0.032007 s
* Elapsed time: 0.035123 s
* Elapsed time: 0.032473 s
* Elapsed time: 0.033759 s

• Wow that's comprehensive. I'm on windows and am going to take some time to work out a shell equivalent - but am marking as the accepted answer in the interim. – Aubrey Blumsohn May 14 '15 at 8:33
• @AubreyBlumsohn I am working on a more elaborate version including a small C program to reduce the runtime of the external program. – Heiko Oberdiek May 14 '15 at 10:24
• @AubreyBlumsohn Running the Perl code from the command line is quite tricky because of quoting problems. The outer layer of double quotes are required by XeTeX to support spaces. But the implementation prevents, that the double quote can be used inside the program call which is quite bad here. In Linux I can use single quotes for the command line argument for the Perl run option -e and the Perl language operator qq//` for double quote strings. On Windows it might be easier to use an installed external program without the need for further quoting, when calling the program with options. – Heiko Oberdiek May 14 '15 at 10:29