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Re: Mathematica 8 remote parallel kernels

  • To: mathgroup at smc.vnet.net
  • Subject: [mg120641] Re: Mathematica 8 remote parallel kernels
  • From: "Oleksandr Rasputinov" <oleksandr_rasputinov at hmamail.com>
  • Date: Sun, 31 Jul 2011 23:37:21 -0400 (EDT)
  • Delivered-to: l-mathgroup@mail-archive0.wolfram.com
  • References: <j0truv$d50$1@smc.vnet.net> <j13e3u$52e$1@smc.vnet.net>

On Sun, 31 Jul 2011 12:25:50 +0100, Iv=E1n Pulido Sanchez  

<ijpulido.s at gmail.com> wrote:

> On Sat, Jul 30, 2011 at 5:00 AM, Oleksandr Rasputinov <
> oleksandr_rasputinov at hmamail.com> wrote:
>
>> Perhaps you are exceeding your quota of kernel licences? (Particularly
>> likely on a shared server where others may or may not also be using some
>> of the available licences at any given time.) Another possibility, if 
>> you
>> are trying to launch a large number of parallel kernels, is that you are
>> running into some kind of limitation on the number of concurrent TCP/IP
>> connections.
>>
>> Other than that, it is likely platform-dependent, but you do not mention
>> what platform you are using. Correctly setting up Windows
>> client-to-Windows server parallel kernel operation is slightly more
>> difficult than for the other platforms, for example.
>>
>
> Thanks for the ideas. And you are right I should've mentioned the OS it's
> running on. It's Linux (Debian Squeeze to be exact).
>
> I don't think it's a license issue since I can run on each node 4
> Mathematica Kernels without problem, the problem is making them process  
> in
> parallel (meaning parallel remote kernels).
>
> This used to work just fine with mathematica7 (Over 20 kernels without
> problem, now I can't get more than 10 in the best case) no idea what  
> could
> have changed with mathematica8.
>
> I've tried manually running the kernels with the ssh command that is  
> shown
> in the Parallel Kernel Configuration dialog without success (Link names
> problems and such). If you could help me with this it would be very mu
ch
> appreciated since this could lead to solve the problem.
>
> Thanks again for your response.
>

I'm afraid I can't reproduce your problem--at least not on Xubuntu 10.04,  
where I can launch at least 24 subkernels via ssh without any  
difficulties. Perhaps a firewall or networking stack setting is limiting
the number of simultaneous half-open TCP connections? Are you able to  
start all of the kernels if you launch them a few at a time, e.g. using

LaunchKernels[
  {SubKernels`RemoteKernels`RemoteMachine["hostname", 4]}
  ]

with the hostname of one of the nodes being substituted at each iteration?

Alternatively, if the nodes are heavily loaded and take some time to start  
the kernels, you may run into the MathLink timeout of 15 seconds. Starting  
fewer kernels at once may also help in this situation.

>> On Fri, 29 Jul 2011 09:45:19 +0100, Iv=E1n Pulido Sanchez
>> <ijpulido.s at gmail.com> wrote:
>>
>> > Hello,
>> >
>> > When I try to configure remote kernels in Mathematica via
>> > Evaluation>Parallel Kernel Configuration ... then I go to "Remote
>> > Kernels"
>> > and add hosts, after that I try to Launch the remote kernels and only  
>> 
>>
>> > some
>> > of them get launched (the number of them varies),and finally I get a  
>> msg
>> > like the following.
>> >
>> > KernelObject::rdead: Subkernel connected through remote[nodo2] appears
>> > dead.
>> >>> LinkConnect::linkc: Unable to connect to
>> >>> LinkObject[36154 at 192.168.1.104,
>> > 49648 at 192.168.1.104,38,12]. >> General::stop: Further output of
>> > LinkConnect::linkc will be suppressed during this calculation. >>
>> >
>> > Any ideas how to get this working?
>> >
>> > Take into account it sometimes does load some of the remote kernels
>> but
>> > never all of them. Thanks in advance I hope you can help me with this.




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