Build server considerations

[Dominic Baines]

Bryan J. Welch wrote:

> I've been asked to investigate Beowulf systems as possible future build
> servers.  We're currently using a Sun Enterprise 6000, so I'm considering
> putting together DEC Alphas or PCs to a faster (and more reliable!)
> machine.
>
> One question I've been asked (and haven't seen in the archives yet) is if
> the code needs to be changed to take advantage of Beowulf's parallelism.

Yes it does.

If we use gcc to build the same code as before on a Beowulf system, will

> we see maximum benefits?

No, and yes. The code can be the same as single CPU code when you are at the
smalleststep in the program but to make maximum use of a cluster you need to
parallelise your
code. Simply put what you do is use either MPI or PVM with associated calls
to it's libraries
in your code to pass the code and data from one CPU to another. (use egcs as
well incidentally it's
better than gcc)

>  Does the code need to be customized somewhat to
> take full advantage, or should I think of Beowulf as simply a faster
> build server and nothing more?

Beowulf uses the concept of parallelisation to make it 'work' faster by
splitting up the codeso that each node takes a part and then you combine it
after processing. You are not simply
multiplying the overall speed by the number of processors, it doesn't work
that way.

If you have questions email me.

> thanks,
> Bryan
>
> --
> Bryan Welch - Bell Labs - bjwelch@bell-labs.com - N0SFG - PP-ASEL

Dominic Baines
IT Manager
University Centre
Cambridge University