Opened 8 months ago

Last modified 8 months ago

#2791 new help

Optimal cycling/queueing/wall-clock time

Reported by: charlie Owned by: um_support
Component: UM Model Keywords:
Cc: Platform: NEXCS
UM Version: 10.7

Description

Hi,

Sorry to bother you, but now that (I think, at least) my Eocene simulation is stable (achieved by reducing the ocean timestep down to 30 minutes), I was hoping you could offer some advice on optimal cycling/queueing/wall-clock time on NEXCS, in order to get the best and fastest runtime?

I am currently using 3 month cycling in the long24 queue, requesting 20 hours of wall-clock time. This is far more than I need, but was because I initially started with a 5 minute ocean timestep which was SIGNIFICANTLY slower. Using 30 minute timestep, it appears to be running the coupled app (of 3 months) in ~1.7 hours, and then the rest i.e. postprocessing and pptransfer in another ~1 hour. By my calculations it appears to be doing the whole 3 month cycle in just under 3 hours.

Using this queue, however, appears unbelievably slow - looking at my last cycle, for example, it was submitted at 14:45 hours on 24 February, but only actually started at 04:26 hours this morning - almost 62 hours in the queue?! Is there no way I can do better than this?

What is the best combination to have i.e. longer cycles to allow less queueing time, or requesting less wall-clock time? Given that it can do 3 months in just under 3 hours, which = 1 year in just under 12 hours, would it be appropriate to do 2 year cycling and request the full 24 hours wall-clock time? Or would it be better to request less wall-clock time (e.g. 15 hours) and do 1 year cycling?

Please can you advise?

Charlie

Change History (2)

comment:1 Changed 8 months ago by grenville

Charlie

The queue time for your job will be influenced by what other jobs have run under nexcs-n02, so I can't say which configuration will give faster turn around - it all depends on usage of the account (and on the machine more widely).

Only time on the parallel nodes has much queuing impact- so only use wallclock for coupled when requesting time. I'd say your model runs 3 months in 1.7 hrs.

Grenville

comment:2 Changed 8 months ago by charlie

Hi Grenville,

Sorry, but I don't entirely understand. Can you explain a little more?

Charlie

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