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To PVM or not to PVM
| To PVM or not to PVM [message #41868] |
Mon, 06 December 2004 16:53  |
Robert Barnett
Messages: 70
Registered: May 2004
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Member |
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Hi,
This post is about Parallel Virtual Machine (PVM). PVM is useful for
creating distributed computing clusters. Using clusters a high
computational load can be split up amongst many processors on a network.
More information about PVM is avilable from
http://www.csm.ornl.gov/pvm/pvm_home.html.
PVM comes with a C library. However, the closest thing I have found to a
IDL dynamically loadable module (DLM) is at
http://www.kilvarock.com/software/idltopvm.htm. PVM is completely
different to IDLs multi-threading. In fact it has been argued that IDL
is not suitable for clustered applications. Details about IDL and
Multithreading are outlined at
http://www.rsinc.com/services/techtip.asp?ttid=3252
I've written a distributed computing application which just plays
musical chairs with sav-files and raw-data files. I've been meaning to
use PVM for some time, but it doesn't seem like it's worth the effort.
Some of the problems with PVM be appear to be:
* I have to compile and set up PVM independantly for each platform.
* PVM requires rsh or ssh. Neither are built-in services provided by
windows workstations
* There is no published DLM wrapper for the PVM C library.
I don't know a great deal about distributed computing. Most people
cringe at my solution.
My solution is based on a master/slave model, where the master creates
jobs for the slaves to do.
* I have a script which accepts socket connections from any
slave/master. This script manages how jobs are received from the master
and distributed amongst the slaves. It does not actually transfer data.
The script is written in a language which is able to handle multiple
threads (currently python but there is also a perl version).
* The actual data is sent between each machine using FTP (passive
connections). The master has a FTP server with files stored on the ramdisk.
There is maximum overhead of 100ms (on client) per interprocess signal.
Most of that overhead appears to be opening a new socket and sending the
(small amount of) data via passive FTP. Given the nature of my project,
this overhead is not of much concern (about 10% of total computation).
To make the solution completely cross platform, I went for FTP rather
than a NFS or Samba drive.
Are there any reasons why I should be using PVM? Has anyone has notable
success in using PVM and IDL in an inhomogenous network? Is this a good
method for setting up a prototype distributed computing application?
Would anyone be interested in my adapting the code for public release?
Cheers,
--
nrb@
Robbie Barnett
imag
Research Assistant
wsahs
Nuclear Medicine & Ultrasound
nsw
Westmead Hospital
gov
Sydney Australia
au
+61 2 9845 7223
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