[MITgcm-support] asyncio

[Dimitris Menemenlis]

Hi Ryan, in theory code-async should work on any lustre file system that is similar to
the one used on pleiades.  In practice it has only been tested on pleiades, so there
will probably be a little trial and error in porting.

For LLC_1080 and a decent file system, you probably don’t need code-async.
I have run LLC_1080 and also LLC_2160 on pleiades with standard useSingleCpuIO
and it run OK for 1080 and OKish for 2160.  For LLC_4320, the I/O got bogged down.

useSingleCpuIO uses mpi routines to do all the I/O from the head node.

code-async reserves a number of additional cores (~3 to 10% on top of those used
by MITgcm computational cores) for I/O only.  As the code runs, these I/O
cores collect the output from MITgcm asynchronously and then take care of
writing it to lustre file system.  so the I/O does not add any additional time to computation.

Dimitris Menemenlis

> On Oct 18, 2016, at 9:30 AM, Ryan Abernathey <ryan.abernathey at gmail.com> wrote:
> 
> Hi,
> 
> What is the deal with the code-async folders in the llc_hires setups?
> http://mitgcm.org/viewvc/MITgcm/MITgcm_contrib/llc_hires <http://mitgcm.org/viewvc/MITgcm/MITgcm_contrib/llc_hires>
> 
> I am working on setting up an LLC_1080 run. The examples in the readme files all include building with this extra code directory.
> 
> What does it do?
> 
> Does it only work on pleiades?
> 
> Cheers,
> Ryan
> 
> 
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