Hi Jason,
> This is probably a rather naive approach, but what's wrong with running
> the
> tests without the switch, then trigger it for production runs after you
> know
> everything else works. Production runs are looking for reproducibility
> of
> ensemble properties rather than making sure the first 100 steps are
> numerically reproducible, anyway, so I don't really see the conflict...
> (obviously the switch will have to be off to validate changes, but
> that's
> easy enough to do)
This is exactly what I planned to do and why it would be a ctrl namelist
option as a 'tuning' parameter. In fact I planned to just enable it if you
set ig=-1. The part that everyone is missing here though is that this,
dealing with if statements, putting it in a namelist, having the test cases
run with the synchronization etc is the EASY bit.
The part that NEEDS to be done first is exactly what you state above. That
production runs are looking for reproducibility of ensemble properties. This
should be tested BEFORE this option is made available. Hence why it is an
undocumented ifdef right now. It is no good just saying the random number
generator works blah blah blah. Someone should actually test if using a
bunch of random number streams with ig=x, x+1, x+2 to x+nthreads-1 works
correctly and gives equivalent ensemble properties. If it these tests all
work then we can enable this as a real documented option.
This is why I say "caveat emptor". This approach has had NO testing except
for performance.
All the best
Ross
/\
\/
|\oss Walker
| Assistant Research Professor |
| San Diego Supercomputer Center |
| Tel: +1 858 822 0854 | EMail:- ross.rosswalker.co.uk |
|
http://www.rosswalker.co.uk |
http://www.wmd-lab.org/ |
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Received on Wed May 12 2010 - 09:30:08 PDT
