[Dev-luatex] Some non-deterministic behaviour i luatex

Lars Hamren tex-6828 at sdu.se
Sun Sep 4 20:04:30 CEST 2016


I started running the context test suite as a regression test to verify that
my local changes don't introduce any errors. I got LOTS of errors. While
I may have introduced som errors, I really couldn't have introduced THAT many
errors. Testing was also somewhat erratic. Sometimes things worked, sometimes not.

So I then ran the test suite using the unmodified standalone context, with
the original binary.

I ran the test suite eight times, and then compared each run with the previous,
so there are seven comparisons for each test.

For each test, I then counted the number that were different.

Ideally, there should either be no differences,
or, if the test uses random numbers, seven differences.

But there are a number of tests that generate between one and six errors.
In total, 324 of the tests do not consistently generate identical output.

I have put an archive of context diffs less than 100k is size here:


There is also the script that I use to compare two runs on the test suite.

Note that I remove a few lines that always differ.
In addition I remove some XML lines.

Each test is run like this

     context --silent --result=/path/to/output/01/cld/functions-001.pdf functions-001.tex

I have identified a few different errors, and will describe them in separate posts.


Lars Hamrén              WWW...: www.sdu.se
Vadmöllan 211            Mobile: +46(705)189090
S-225 94 Lund

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