Surprised? NOT!

Posted Apr 12, 2004 22:19 UTC (Mon) by josh_stern (guest, #4868)
In reply to: Surprised? NOT! by AnswerGuy
Parent article: Cray CTO: Linux clusters don't play in HPC (Search Enterprise Linux)

Code has to be modified in one way to take advantage of clusters and
it has to be modified in a different way to take advantage of SMP
style computers. That's it, they're different...and tool support
is probably better for doing CASE-based SMP...and the Cray guy wants
to equate HPC with SMP. Give him credit for not trying to hide the
fact that clusters are a much cheaper way to get a given quantity
of compute power.

Ehm...

Posted Apr 13, 2004 7:05 UTC (Tue) by Los__D (guest, #15263) [Link] (4 responses)

Not completely true... An app for a beowulf cluster needs specific teqhniques and libraries, but an openmosix cluster can speed up any SMP-capable program... Off course there's apps that can use the mosix cluster better than others, but as a base argument it uses the cluster without special programming.

Dennis

Ehm...

Posted Apr 13, 2004 16:13 UTC (Tue) by evgeny (subscriber, #774) [Link]

> an openmosix cluster can speed up any SMP-capable program

Don't take your dreams for reality. From http://howto.ipng.be/openMosixWiki/index.php/FAQ:

[...] openMosix can't (as of yet) migrate threaded programs. If you want a single task to run on multiple machines simultaneously, you'll have to use fork() to create multiple processes.

Ehm...

Posted Apr 13, 2004 16:20 UTC (Tue) by josh_stern (guest, #4868) [Link] (2 responses)

Mosix didn't previously support shared memory in any meaningful way:

http://sourceforge.net/docman/display_doc.php?docid=10390&group_id=46729

Has that changed now that Linux 2.6 has NUMA support?

What I really meant above is that one will optimize
an algorithm in a different way depending on whether data sharing
happens by a) address mapped to fast (real) memory, b) address mapped
to slow (disk) memory, or c) explict message update. For distributed
systems, a) and c) are more similar in performance
characteristics while a) and b) are similar in what the code looks
like. So each of three differ in at least one important way, and
Cray, historically emphasized a).

It's true that Beowulf has a lot more mindshare than Mosix for
no rational reason.

Ehm...

Posted Apr 14, 2004 4:03 UTC (Wed) by sitaram (guest, #5959) [Link] (1 responses)

> Mosix didn't previously support shared memory in any meaningful way:

http://mcaserta.com/maask/

I must admit I dont know what the official status of that patch is, though.

Ehm...

Posted Apr 14, 2004 7:40 UTC (Wed) by josh_stern (guest, #4868) [Link]

Very interesting! Include the fact that it was created
by five female Indian undegraduates as a senior project!