[FLASH-USERS] Big Problem??

[Tomasz Plewa]

Seyit -

>> If you run in parallel, can you confirm that the results differ when 
>> you run on a single processor?
> 
> Quick answer, yes. If I run with multiple processors instead of 1, the 
> results do differ!

The idea is to narrow the number of options you use. If serial execution 
  produces consistent results, you have a good basis to start. For one, 
such consistency may indicate that your compilers produce fair results.

>> If you run on many levels, how about a single block/level solution?
> 
> I should try that. But I assume they might differ also, since 1 of the 
> three computers started directly with a different dt_hydro. I'm not sure 
> if that would matter.

Information is generally helpful, but since we are in murky waters then 
not just any information is equally helpful.

If you try a single block, you eliminate perhaps 90% of the code 
complexity.

> I know for a fact that choosing gamma 1.001 works on one computer and 
> not on the other (Vcycle problem). Guess it's a too small value.

Try a single block first, if possible. If results do differ before 
evolution starts (initial time step differs), there is a problem with 
initilizing your application. This will narrow your focus to perhaps 1% 
of the code.

Tomek
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