[Beowulf] RDMA NICs and future beowulfs

Ben Mayer bmayer at gmail.com
Tue Apr 26 08:01:25 PDT 2005

Just a quick comment about CELL and gcc and vectorizing.

I looked over the specs of CELL and it looks very much like a hybrid
vector processor. gcc now has support for vectorizing (some) loops.

I spend a good deal of time writing code for Cray X1Es (vector
supercomputer), and there are a lot of things that can trip up a
compiler when one is trying to get it to vectorize code. I actually
just did a small study of how well students in a parallel computing
class write parallel codes on X1 with MPI and UPC. One of the things
that stood out is that they tended to do odd things in their loops
that inhibit code from vectorizing.

Writing code which vectorizes well is difficult. The reason I mention
this is that, I believe, we will see that someone *has to* produce
libraries (or entire engines) that take advantage of the Cells unique
layout to get decent performance. If there are major parts of the code
which can not run in parallel (Vectorization is a type of parallel
execution) Cell is just a crummy PPC chip.


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