[MITgcm-support] convincing compiler of node memory size

[Constantinos Evangelinos]

On Thursday 15 April 2010 13:33:40 Matthew Mazloff wrote:

> Level 1 is stored in local cpu/node memory, while Level 2+ are written
> to external disk.  You can optimize your run efficiency by choosing a
> level 1 size that uses all available cpu memory.  (This is what Holly
> is trying to do.)

Exactly. It's an optimization problem
L1*L2*L3*L4 >= # of timesteps
max L1 fit in memory
min (L2+L3+L4) to minimize disk usage. 
BUT if you can spare the disk space, then drop L4 to gain speed (and if you 
can really spare the diskspace drop L3 also to gain even more speed). In fact 
if you have a machine where you can take L1 to very large numbers (lots of 
available memory per process, an L1,L2 scenario is the fastest.

Constantinos
PS> Also beware of netcdf linking problems when using -mcmodel=medium. 
-- 
Dr. Constantinos Evangelinos
Department of Earth, Atmospheric and Planetary Sciences
Massachusetts Institute of Technology