Feature request: speed-up Sphinx build of LaTeX files

[jfbu]

When building Sphinx own documentation at my locale, it currently needs about 12.5s for the HTML build, and about 57s for the PDF build. From this, about 48s are needed for Sphinx build itself and 9s for pdflatex producingt PDF from the LaTeX file. Most of the 48s are spent into the "writing phase".

Perhaps there is something suboptimal here and it should be made faster if possible.

Environment info

• OS: Mac OS 10.9.5 on a 2,8 GHz Intel Core i7 with 16 Go 1333 MHz DDR3 memory
• Python version: 3.6.4
• Sphinx version: 1.8.0+/9a2092759
• TeXLive 2018 with self-built binaries

[tk0miya]

I investigated it with following patch:

diff --git a/sphinx/builders/__init__.py b/sphinx/builders/__init__.py
index 9c1c50c5b..6a25c2db5 100644
--- a/sphinx/builders/__init__.py
+++ b/sphinx/builders/__init__.py
@@ -396,7 +396,12 @@ class Builder(object):
         self.finish_tasks = SerialTasks()

         # write all "normal" documents (or everything for some builders)
+        from cProfile import Profile
+        p = Profile()
+        p.enable()
         self.write(docnames, list(updated_docnames), method)
+        p.disable()
+        p.dump_stats('writing.prof')

         # finish (write static files etc.)
         self.finish()

And I got the following profile. It says renumber_footnotes is a very slow.

   ncalls  tottime  percall  cumtime  percall filename:lineno(function)
        1    0.000    0.000  113.261  113.261 /Users/tkomiya/work/sphinx/sphinx/builders/latex.py:115(write)
        1    0.001    0.001  109.959  109.959 /Users/tkomiya/work/sphinx/.tox/py27/lib/python2.7/site-packages/docutils/writers/__init__.py:65(write)
        1    0.000    0.000  109.949  109.949 /Users/tkomiya/work/sphinx/sphinx/writers/latex.py:178(translate)
11856071/1346   43.959    0.000  108.620    0.081 /Users/tkomiya/work/sphinx/.tox/py27/lib/python2.7/site-packages/docutils/nodes.py:207(traverse)
        1    0.000    0.000  108.001  108.001 /Users/tkomiya/work/sphinx/sphinx/writers/latex.py:233(apply)
        1    0.010    0.010  107.873  107.873 /Users/tkomiya/work/sphinx/sphinx/writers/latex.py:286(renumber_footnotes)
 84801230   24.936    0.000   24.936    0.000 {isinstance}
12398557/1083   16.669    0.000   21.848    0.020 /Users/tkomiya/work/sphinx/.tox/py27/lib/python2.7/site-packages/docutils/nodes.py:190(_fast_traverse)
 18363833   14.712    0.000   21.496    0.000 /Users/tkomiya/work/sphinx/.tox/py27/lib/python2.7/site-packages/docutils/nodes.py:565(__getitem__)
      264    0.046    0.000   21.067    0.080 /Users/tkomiya/work/sphinx/sphinx/writers/latex.py:288(is_used_number)
 11809912    4.925    0.000    9.209    0.000 /Users/tkomiya/work/sphinx/sphinx/writers/latex.py:305(is_footnote_ref)
        1    0.000    0.000    3.221    3.221 /Users/tkomiya/work/sphinx/sphinx/builders/latex.py:169(assemble_doctree)

[tk0miya]

Fixed by #4843
Thank you always!