Hi Prathap,

That sounds very odd and should not happen unless the workload itself is 
somehow random. What is it you are running? Are you sure you’re running exactly 
the same thing?

If it does indeed vary then it would be good if you can track down why by 
running two simulations in lock-step and determining where they diverge.

We regularly run the ARM regressions with UBSan to ensure there is no undefined 
behaviour in the simulator. I know that for X86 there are quite a few warnings 
from UBSan, so that could be a reason if you’re using x86.

Andreas

From: gem5-users 
<[email protected]<mailto:[email protected]>> on behalf of 
Prathap Kolakkampadath <[email protected]<mailto:[email protected]>>
Reply-To: gem5 users mailing list 
<[email protected]<mailto:[email protected]>>
Date: Thursday, 13 August 2015 09:11
To: gem5 users mailing list <[email protected]<mailto:[email protected]>>
Subject: [gem5-users] Sources of In-determinism in Full System Simulators

Hello User,

I am running a benchmark in gem5 full system mode. Checkpoint is created in 
atomic mode and then switches to detailed mode before starting the benchmark. 
On repeated  runs of the benchmark from same checkpoint, the number of memory 
requests arriving at DRAM banks differs; up-to 5% variation.  Can someone point 
out, what could be the sources of in-determinism?


Thanks,
Prathap

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