Re: Parallelization on Dell Workstations

Ganesh <ganesh.iitm@xxxxxxxxx> writes:

Ok.. we are not planning to connect these machines together.. ! The
codes are going to be run on individual comps only !

So we're talking only about SMP parallelisation.

However.. I have had trouble understanding the architecture of these
computers. Take for e.g a Dual core machine (one that is commonly
available for desktops these days). Is the memory shared between these
cores ? How about the cache ?

The main memory (RAM) is shared among all cores. The cache sharing
depends on the architecture, Intel's Core2 Duo has per-core L1 caches,
but a shared L2 cache while the AMD dual-cores have separate cache
hierarchies.

Going further..! What happens in these high end workstations ? Take
for instance the Double Dual core, and the double Quad core.. ! The
link has i sent has all the info. However I am not able to comprehend
them fully.

What do you mean by »happens«? In the case of a double quad-core
machine, you would have two processing modules with four cores each; for
most of your work you treat them like a simple 8-way SMP system.

I have an MPI code working. Setting up OpenMP code is not that big a
deal I guess. A combo would involve some effort as well. I am ready to
put in the effort needed. However I need to know which one to put my
effort on ?

Good MPI implementations should realise intra-node communication via
shared memory, so you pay a bit of lost efficiency due to the messaging
overhead. For the moment, I would suggest to install an MPI library and
run your code; you should do profiling runs and determine the
bottlenecks (communication? computation?).


Sebastian
.

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