Dear Vadim,

On 2/14/07, Vadim Ogranovich <[EMAIL PROTECTED]> wrote:
> Hi,
>
> I have few high-level questions about the Snow and Rmpi packages . I 
> understand that Snow uses Rmpi as one of possible transport layers, yet my 
> questions about user experience, not technical details:
>
> 1. Does Snow install and work well in Windows?
> 2. Interruptibility. I understand that currently it is impossible to 
> interrupt a running top-level command in Snow ( Ctl-c or the likes), the only 
> way to kill slave processes is to kill the master R process. Is this 
> accurate? What about Rmpi ? Is there any difference between Windows and Linux?


I've never used any of those under Windoze. I think your statement is
accurate under Linux. (In fact, I often get rid of any of those Rmpis
gone astray by issuing a lamhalt and/or lamwipe).

> 3. When the master process dies , is it guaranteed that the slaves will die 
> too? How reliable is this (I've seen some applications, not related to R, 
> that were flaky about killing slaves)


If you use an orderly exit procedure (mpi.close.Rslaves(); mpi.quit())
I've never, ever, seen badly behaved Rmpi slaves. But I've seen them
under strange circumstances (I think network problems that messed up
the lam universe ?).

A kind of fail proof approach, if you can afford it, is to use
different lam universes (using the LAM_MPI_SESSION_SUFFIX) for
different simultaneous runs. Then, if one particular run behaves
poorly, you can issue a lamhalt/lamwipe for just that LAM universe.

A final suggestion: you might want to take a look at the papply
package, which does load-balancing and allows you to run sequential
(if there is no lam universe), and thus makes debugging much simpler.

R.


>
> Thank you very much for your help,
> Vadim
>
>
>
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>
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>


-- 
Ramon Diaz-Uriarte
Statistical Computing Team
Structural Biology and Biocomputing Programme
Spanish National Cancer Centre (CNIO)
http://ligarto.org/rdiaz

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