Hi,

I'm running Linux on a laptop with 2Gb RAM and a dual core processor:
GenuineIntel Intel(R) Core(TM)2 Duo CPU T5670 @ 1.80GHz [Family 6 Model 15 Stepping 13]


I've been happily running two climate models simultaneously for a while, but this doesn't seem to work with two HADAM3P models - my system starts to become very unresponsive, locking up for minutes at a time.

I notice that HADAM3P models use approximately 4 times as much RAM as some other models, and I believe I read somewhere that these models to a great deal of memory manipulation. I assume that this is the cause of my issue, but I just thought I'd write about it here to let people know about the problem and perhaps get someone to confirm it.

For the time being I've set my preferences so HADAM3P models aren't run at all, which seems to have cured the problem. However, I'd be interested to know if there's a way to set my preferences so that one HADAM3P model can run, but not two.

Thanks in advance,
Steve.

Steve,

There is a thread here that discusses the performance of multiple HADAM3P models.

As for tuning the preferences, you can:

1. Select a mix of model types, and over time you'll get a mix. Some of the time, however, you'll get two HADAM3Ps.

2. Get one HADAM3P running (by limiting the number of CPUs), then change the model preference to some other model type (locally is easiest), increase the number of CPUs, and get another model for the other core. That's a bit labour-intensive though, particularly as the HADAM3P models are short by CPDN standards.

Iain

I prefer to keep a base load of HadCM3L tasks on my systems (dual and quad core) and find it very easy to restrict them to a single HadAM3P task at a time.

My project preferences are normally set to allow only HadAM3P tasks but when a HadCM3L task has less than a week to run (connection interval is set to 1 day) I switch my preference over to HadCM3L until one is downloaded and then switch back to HadAM3P. There's a couple of ways of working this:

• modifying the project preferences directly.
  
  
• setting up 2 project preference venues and altering the computer's venue every time you want to switch its preferred task type.
  

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"The ultimate test of a moral society is the kind of world that it leaves to its children." - Dietrich Bonhoeffer

Hi Steve

HadAM3Ps seem to do a lot of memory swapping. On most multicore computers this means that running too many of them simultaneously slows all of them down because they compete for a resource. This is a known problem and we've warned about it in the News thread (top of Number Crunching & link in my signature). I don't remember reading reports that too many HadAM3Ps run simultaneously can slow a whole computer down but I believe it.

You will probably find that when you run a HadAM3P together with another model type the HadAM3P runs faster.

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Cpdn news

Thanks for the replies. It didn't occur to me to look in the number crunching forum for some reason. It would have saved you all some posting time!

I have experimented with running one HADAM3P model alongside a different model, and it works just fine. However, since I'm lazy, I'll just let my dual core machine run other models, and my single core machine can continue to run HADAM3P models as it seems to be fine with that.

Steve.