Re: [Bug-gnubg] Threaded rollouts and RNGs

[Ian Shaw]

Hi Øystein,

 

My understanding, which is very old, is that it is threaded on the rollout candidates. In-game move evaluations are not threaded.

 

But Phillippe has done a lot of work since then ,so it may have changed.

 

n  Ian

 

From: Bug-gnubg [mailto:bug-gnubg-bounces+address@hidden On Behalf Of Øystein Schønning-Johansen
Sent: 01 February 2017 10:11
To: address@hidden
Subject: [Bug-gnubg] Threaded rollouts and RNGs

 

Hi!

 

It's a long time since I browsed the GNU Backgammon code now. :-)

 

The rollout code in GNU Backgammon is of course threaded. How is this threaded actually? Is it threaded on each sample (aka each game). One thread pr. game? Or one thread pr. evaluation? Or?

 

I just wrote a code that does a threaded MC simulation of a different problem, and I noticed that I got significantly different results depending on either I used threading or not. Funny thing, it didn't initially occur to me, but of course I need one separate RNG instance for each thread. Fixing that didn't only give me the right results of the simulation, but it also improved the performance.

 

How about GNU Backgammon? Do you use one separate RNG instance for each thread?

 

best regards,

-Øystein