[pdftex] pdftex deterministic?

[Martin Schröder]

2007/4/3, Matteo Centonza <matteo at metatype.it>:
> Using checksums is the cheapest way of comparing two files
> (even cheaper than a byte comparison) and give you absolute
> confidence on the result.
>
> The only drawback is that you have to slightly modify the driver
> in order to make this possible (e.g. fixing IDs differences)
> but this could be an explicit option given to pdftex to let
> it strip runtime info and focalize on the content. For
> final production files you have simply to rerun pdftex
> with this options turned off.

You can do this now if you reset your system date for each run of
pdftex -- but I agree that that's not very practical.

The problem with comparing pdfs by byte is that in the end you don't
want compatibility by byte: You want identical output and you don't
care if e.g. the fonts have a different way of being subsetted. And
the only way to test for identical output is to rip the pdfs and
compare the resulting files.

Best
   Martin