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Re: [Condor-users] Parallel Computing Using Globus and Condor

On Sat, 01 Oct 2005 Natarajan,Senthil wrote :
>I am planning to do the Parallel Computing (Grid Computing) using the
>Globus and Condor.
>I just want to find out is it possible to do the following.
>1) If I submit a job either to Globus or directly to condor. The job has
>to be divided (either by globus or by condor) and sent across different
>available resources (nodes) and collects the results, combine and send
>the combined result back to the client. That is for example if a job
>takes ordinarily 10 mins, if the same job submitted in the above
>scenario I like to see definitely less than 10 mins say may be 5 mins
>suppose if the job is divided across 5 resources.

Ans> That depends on You. If you have written MPI/ PVM program, you can very much run it across multiple machines on cluster, prvoided you have specified no of m/cs in submit file "concept of condor". But say if its a nonMPI/PVM job, still you can run it in parallel on multiple machines, with some extra care(Like in this case you have to specify 5 copy of executables to run on 5 different machines). Collection of results wud be per machine based and it would be collectively stored on from where u hav submitted job. To coalate 2 1 file, you wil hav 2 write some specialized script. And definitely time factor wud be reduced wen spanned across multiple machines.

>2) Does the globus or condor will automatically do this for us, or do we
>need to write a separate program to do this or the job it self should be
>written in special way to accomplish this.

Ans. Job should be written such a way that is should run in parallel if its a MPI/ PVM. If its not MPI/PVM, its upon you how you decide.

>3) Does the cluster will divide and send the job across its nodes and
>collect the result and send the combined result back.

Ans. Condor shud b told in advance wat it needs to do.  For dat u wil hav 2 write submit file, where you wil have to say the job type (MPI/ PVM/ Standard/ Vanilla/ Parallel/ Java), no of machines (if MPI/PVM), environment settings, Input/ Ouptout files etc.

>4) What is MPI, MPICH and what for it has been used.
Ans. MPI is Message Passing Interface basically a library to write parallel programs. Its a well-known standard. However MPICH, LAM are implementations based on MPI Standards!!!