[tex-live] [XeTeX] Random number primitives

David Carlisle d.p.carlisle at gmail.com
Mon Nov 14 10:07:56 CET 2016

On 13 November 2016 at 16:50, Apostolos Syropoulos
<asyropoulos at yahoo.com> wrote:

> OK please let me know how the pdftex thing is implemented and I will do the
> thing with drand48. Then people can check the implementation, etc.
> A.S.

People using a fixed seed to get reproducible results would not be
well served by a change in the random number generator. Just because
something would be easy to change doesn't mean that change is always a
good idea.

A document using a fixed seed would have been generating reproducible
results with pdftex since these functions were added more than ten
years ago.

Changing the source isn't the issue, are you offering also to help
with user support to manage the change
and explain to people why it's not possible to re-create documents
that they created before they updated
their tex system?

That said, if you want to look, the version in pdftex is

@* \[7b] Random numbers.

starting at line 2507 of  source/texk/web2c/pdftexdir/pdftex.web

Sometimes change is necessary but here it really isn't clear that the
statistical properties of drand48 are superior to Knuth's algorithm
from metafont  (I've never seen any comparison of these, only between
drand48 and C rand)
Or whether any of these algorithms have any real flaws when used with
sequence lengths of the sort realistically
practical in a tex document.


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