How does that work?
The binaries have to get the all the machines of the clusters
somewhere.
Does this assume you are using NFS or similar for your build
directory?
Won't the overhead of using that instead of local disk kill most
of the
parallelization benefit of a cluster over a single SMP machine?
This will be true regardless of communication method. There is so
little
opportunity for parallelism that anything more than 4-8 local cores is
pretty much wasted. On a 4-core machine, more than 50% of the wall
time
is spent on things that will not use more than those 4 cores
regardless.
If the other 40-50% or so can be cut by a factor 4 compared to 4-core
execution, we still are talking about at most a 30% improvement on the
total wall time. Even a small serial overhead for communicating
sources
and binaries will still reduce this 30%.
We need to improve the Makefiles before it makes sense to use more
parallelism. Otherwise we'll just keep running into Amdahl's law.