On 4 March 2011 11:30, Volker Braun <vbraun.n...@gmail.com> wrote: > MPI is more comparable to Mathematica's underlying MathLink C libraries. We > also have an mpi4py optional spkg that maps the C to a Python API, > essentially one-to-one. Its not pretty, but if you know MPI then you can > immediately use it. There is a mini-introduction and a sample program at > http://www.sagemath.org/doc/numerical_sage/parallel_computation.html > The @parallel decorator could be extended to optionally use MPI as parallel > processing backend. Right now @parallel(p_iter) supports 'fork', > 'multiprocessing' (threads) and 'reference' (serial execution). It would > then pickle the function and its arguments, MPI broadcast them to the > cluster, execute them as a bag-of-tasks, and finally receive the answer from > the nodes. The only constraint would be that you can't access global > variables on the compute nodes, obviously. As far as I understand it from > the link you posted, this is essentially what Mathematica's ParallelTools > do. > But again, that only works for embarrassingly parallel workloads. If you > need a lot of cluster communication then there is no way around learning > MPI. For example, MPI allows you to > * send/receive without blocking (a background thread deals with the cluster > communication); > * reductions (e.g. each node has a number and you want to add them up) work > in O(log(n)) and not O(n) > * support for fast network hardware (Cray's SeaStar interconnect has more > bandwidth than AMD's hypertransport between CPU and the local RAM!) > Volker
I think in cases like this, the documentation in Sage should make it clear what the package actually does and what needs to be learned to use it. It's easy to jump to the incorrect conclusion that the package will permit existing Sage code to work on a cluster relativelly easily, when in fact that's not the case. Since I understand the Sage optional packages should be supported by the Sage community, as Sage is, then its impossible for people to give any real support if we don't have any documentaiton on them. BTW, I found that OpenMPI builds on both Solaris 10 (SPARC) and OpenSolaris (x86) if I use the Sun compilers, but not if I use gcc. I updated #10866 and #10869 to add this information. Dave -- To post to this group, send email to sage-support@googlegroups.com To unsubscribe from this group, send email to sage-support+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/sage-support URL: http://www.sagemath.org
