[Stellar-discuss] n processors

[Bill Paxton]

On Dec 3, 2005, at 7:14 PM, Frank Timmes wrote:

> one item that hasn't been discussed is if this
> new generation code should be serial or parallel.
> if parallel, do we aim for shared memory or distributed memory
> architectures (e.g., openmp versus mpi or both)?

Hi Frank,

Good point -- and another area where I'm way out of touch with  
current state of the art tools.  Any suggestions for background  
reading for me?  And just to add to the pot, what about the issues of  
dual core processors that share a single cache memory?  Is this  
included in the usual shared memory approaches or does it require  
something special (at the thread level I presume).

Perhaps a reasonable guideline for decisions such as this is what to  
we need in order to make good use of a typical laptop computer  --  
both now and in the next few years.  In other words, we're not  
designing for 3D simulations on a super computer with massive  
parallelism and huge data sharing.  But even our target laptop will  
have soon multiple processors, at least at the "multi core" level, so  
some form of parallelism is certainly attractive.  And the stellar  
evolution problem certainly presents lots of opportunities with  
things like EOS and burning being done in parallel on different shells.

I guess I'm talking myself into a shared memory, multi-threaded  
design.  Are there good tools to support that in Fortran90?  And can  
we do it while still honoring the "trumps-all" principle of KISS?

--Bill