[MITgcm-support] MNC_MAX_ID too small for 24 tiles

[Ed Hill]

On Fri, 2004-12-10 at 18:47 -0500, Matthew Robert Mazloff wrote:
> 
> MNC_MAX_ID = 1000, is hard coded into the model.  However, when I break the
> model into 24 tiles, this value is too small.  Is there any reason why I
> shouldn't change this value to 1500 so I can run the model with 24 tiles?  Why
> is there a max number of allowed indices? 


Hi Matt,

Short answer:

Please go ahead and set MNC_MAX_ID to as big a value as you need.  I'd
increase it by a factor of 10 every time you get an "out of memory"-type
error.  Unfortunately, there is no easy way of knowing exactly how much
memory MNC will need since it depends (to a great extent) upon run-time
variables.


Long answer:

While its very portable, optimizes readily, and can be understood by
essentially all scientists, Fortran77 is *archaic*.  It doesn't (easily)
allow for dynamic memory allocation.  So the sizes of nearly all the
important arrays in MITgcm are set at compile-time.  And despite my
desire to write MNC in C (which supports dynamic memory allocation), the
group decided to use F77.  So, for now at least, thats what we have.

I'm hoping that MITgcm will evolve so that the core routines no longer
rely upon Fortran COMMON blocks.  Perhaps some important new feature or
combination of features will precipitate this change.

Ed

-- 
Edward H. Hill III, PhD
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