[gmx-developers] Shared-Memory Communication & POSIX Semaphores Under OS X

Alex Nicksay online at nicksay.com
Mon Mar 10 06:36:56 CET 2003

Having just joined the list, I'm not sure to who this message should be  
directed, so anyone please feel free to provide some information.

I'm just getting introduced to Gromacs via Stanford's Folding at Home  
initiative.  Apparently, Gromacs is being worked integrated into F at H  
system for their next release, but that's not the question here.  I was  
looking at the Single-Processor Benchmarks page for Gromacs, and I saw  
this note:

> [2] Based on Gromacs-3.1.5_pre1 with improved Altivec assembly loops  
> (ftp.gromacs.org/pub/beta), and gcc-3.1.  PPC version of LAM-mpi was  
> compiled with standard parameters and not optimized for large-size  
> packages. Unfortunately, shared-memory communication does not work yet  
> on OS X, since the system doesn't support POSIX semaphores. The TCP-IP  
> communication is obviously significantly slower, but this will  
> probably improve soon.

Now, I haven't looked through any code yet, nor have I specifically  
confirmed this with my own tests, etc, BUT as far as I know, OS X  
*SUPPORTS* POSIX semaphores.  For quick reference, see:
"System Overview: Sharing Large Resources With Shared Memory"

Can anyone give me some feedback about why the Benchmarks page has a  
note to the opposite?


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