Re: [Gems-users] How to replicate simulation runs exactly

["Fuad Tabba" <fuad@xxxxxxxxxxxxxxxxx>]

I wanted to add that it might be simics that's inducing some randomness rather than gems. Running simics (without gems) with an instruction trace of a multithreaded program twice and diffing the traces shows some differences.

A google search for this issue shows a result for Simics 4 being the "first deterministic multithreaded simulator"....

Has anyone been able to reproduce exactly two multithreaded runs using simics/gems? I've only managed to pull that off if I'm running one processor...

Thanks again.

Cheers,
/fuad

On Thu, Oct 30, 2008 at 10:03 AM, Fuad Tabba <fuad@xxxxxxxxxxxxxxxxx> wrote:

Hi Dan (and everyone else),

Setting the g_RANDOM_SEED to 1 doesn't seem to be working. Two runs of the simulation produce different timing results. I also searched through the code, srandom is always initialized by g_RANDOM_SEED, and I didn't find an instace where setting g_RANDOM_SEED to 0 would result in passing time(NULL) instead of the seed provided... I've also attached gdb to simics/ruby before loading ruby, with breakpoints set on srandom,srand,random and rand to verify that srandom does indeed get the value I've set for g_RANDOM_SEED, and that it gets called before any calls to random, and my assumptions seem to be correct.

I am using GEMS2.1/ATMTP btw...

Any other ideas or suggestions?

Thanks.

Cheers,
/fuad

On Thu, Oct 30, 2008 at 8:21 AM, Fuad Tabba <fuad@xxxxxxxxxxxxxxxxx> wrote:

Thanks Dan.

Cheers,
/fuad

On Thu, Oct 30, 2008 at 4:49 AM, Dan Gibson <degibson@xxxxxxxx> wrote:

RANDOM_SEED = 0 forces a random seed based on the current value of time(NULL). Most PRNGs cannot handle 0 as a seed. Set RANDOM_SEED to non-zero.

Regards,
Dan

On Tue, Oct 28, 2008 at 10:31 PM, Fuad Tabba <fuad@xxxxxxxxxxxxxxxxx> wrote:

Hi,

Running GEMS/ATMTP, if I run the exact same experiment twice, I get slightly different results in timing. Is it possible to replicate the experiments exactly?

RANDOMIZATION is set to false and RANDOM_SEED is set to 0; but still, I cannot replicate the exact timing...

Is there a way of doing this? Thanks.

Cheers,
/fuad

_______________________________________________
Gems-users mailing list
Gems-users@xxxxxxxxxxx
https://lists.cs.wisc.edu/mailman/listinfo/gems-users
Use Google to search the GEMS Users mailing list by adding "site:https://lists.cs.wisc.edu/archive/gems-users/" to your search.

--
http://www.cs.wisc.edu/~gibson [esc]:wq!

_______________________________________________
Gems-users mailing list
Gems-users@xxxxxxxxxxx
https://lists.cs.wisc.edu/mailman/listinfo/gems-users
Use Google to search the GEMS Users mailing list by adding "site:https://lists.cs.wisc.edu/archive/gems-users/" to your search.