Just a little further clarification on the host/ip issue.
I'm using the very useful simple socket client-server framework to run an
evolutionary algorithm written in J on an 80 node unix cluster. The clients
evolve separate populations, the server propagates the current fittest
member across all the clients. The tricky bit is that I have to launch the
server as a batch job, so I don't know ahead of time on what node it will
run. I then launch the clients who each open a socket to the server.
However, the clients have to know the location of the server (so
sdgethostbyname won't work).
The solution that works for me is to get the server to execute:
host =: {: 2!:0 hostname
and write the result to a file along with the port number etc., which is
then read by clients when they launch.
Note that echo $HOSTNAME doesn't work because it seems to pick up the value
from the launching environment (this might also be true if you use getenv).
Also, the curtail ({:) is crucial. The socket opening routine is
unforgiving of the CR that hostname appends to the result (the jconsole
crashes with a broken-pipe error).
Thanks for all the useful feedback, and thanks to Eric Iverson for the
excellent client/server lab and code template.
Ronan
On 17/11/2006 08:22, "Ronan Reilly" <[EMAIL PROTECTED]> wrote:
> Thanks Joey! I'd been looking in the wrong place.
>
> Ronan
>
>
> On 16/11/2006 21:24, "Joey K Tuttle" <[EMAIL PROTECTED]> wrote:
>
>> At 19:20 +0000 2006/11/16, Ronan Reilly wrote:
>>> Hi All,
>>>
>>> I'm running a distributed application on a cluster using J and I need a verb
>>> that returns the IP (or hostname) of the node on which the jconsole is
>>> running.
>>>
>>> Thanks for any help.
>>>
>>
>> Assuming you are in a _NIX environment, 2!:0 (Host) is
>> the key - e.g. I would use:
>>
>> host 'echo $HOSTNAME'
>> focus
>>
>>
>> where host is defined as:
>>
>> host
>> [: 2!:0 '('"_ , ] , ' || true)'"_
>>
>>
>> You might choose to make a simpler verb with just 2!:0
>> but the extra stuff in the above definition makes it
>> more useful in that it always returns a result, even if
>> the expression passed to the host has no result.
>> ----------------------------------------------------------------------
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>>
>
> --
> Professor Ronan Reilly
> Head of Department
> Department of Computer Science
> NUI Maynooth
> Maynooth
> Co. Kildare
> IRELAND
>
> t: +353-1-7083847
> e: [EMAIL PROTECTED]
> w: http://www.cs.nuim.ie; http://cortex.cs.nuim.ie
>
>
>
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> For information about J forums see http://www.jsoftware.com/forums.htm
>
--
Professor Ronan Reilly
Head of Department
Department of Computer Science
NUI Maynooth
Maynooth
Co. Kildare
IRELAND
t: +353-1-7083847
e: [EMAIL PROTECTED]
w: http://www.cs.nuim.ie; http://cortex.cs.nuim.ie
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