[yt-dev] Optionally resetting the random number generator stream in Rockstar

[Matthew Turk]

Hi all,

I've just pushed a change to the fork of Rockstar I have on bitbucket that
adds a default-off compile-time setting that governs whether or not the
random stream is reset following the call to "random_sleep" that governs
how the clients connect to the server.

https://bitbucket.org/MatthewTurk/rockstar/commits/cf88fc3f9c1c9f0768005be5a07f816b0c79aaa8

This addresses something that's come up on this list before.  I think it
should make runs completely deterministic (it does in my case) and will fix
the halo finding and halo analysis tests.  They are now, in my tests,
bitwise identical between runs whereas before I was getting definitely
non-bitwise results.  (This is noted in the paper.)

I wanted to make this a parameter, but I wasn't able to figure out how to
do it without breaking API compatibility.  So eventually, this should make
its way upstream, but for now, it should (if compiled correctly!) fix the
tests.

If you're building rockstar at home:

 RNG_FLAGS=-DRESET_RNG_STREAM make clean lib

should get it for you.

-Matt
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