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Re: [ESPResSo-users] Simulation of fluid using LB-method

From: Wink, Markus
Subject: Re: [ESPResSo-users] Simulation of fluid using LB-method
Date: Mon, 27 Jan 2014 13:07:48 +0000


I hope I understood your point correctly. I have run the script with two calls 
of "integrate 1000", having a box of 50^3 and an agrid of 1, resulting in 
125*10^6 site updates.
It took 22 min 2s for the simulation resulting in roughly 19k SUPS. This is far 
below your expected 10M. I have no clue what the reason for that is.

The binary of Espresso I have created only had "LB", "LB_BOUNDARIES" and 
"EXTERNAL_FORCES" activated.  Running the testscript "lb_planar.tcl" (box of 
length 12, total integrate of 5000) takes about 14 sec, resulting in ~0.6M 
Thanks a lot for your support and best Regards

Markus Wink

-----Urspr├╝ngliche Nachricht-----
Von: address@hidden [mailto:address@hidden Im Auftrag von Ulf Schiller
Gesendet: Montag, 27. Januar 2014 12:16
An: address@hidden
Betreff: Re: [ESPResSo-users] Simulation of fluid using LB-method

On 01/27/2014 11:54 AM, Wink, Markus wrote:
> 3) Even though, the velocity profile saturates, it takes pretty long
> (time scale of days). The saturation sets in at about 350 times the
> "integration 1000" command. This corresponds to a time scale of ms in Si
> units. Besides using OpenMpi or the GPU impementation, is there anyway
> to speeden up the simulation? For example by adjusting the parameter tau
> in the lbfluid command?


that sounds a bit strange to me. If your system is 50^3 and you 
integrate 1000 steps, that gives 125*10^6 site updates. On a reasonably 
modern CPU, a reasonable LB code should get to around 10M SUPS (million 
site updates per second), that is, one call of "integrate 1000" should 
not take much more than 10 seconds, so 350 calls roughly one hour not 
days. Can you check how many site updates per second you get on your system?


Dr. Ulf D. Schiller                        Building 04.16, Room 3006
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