Slow running

MOHID Land forum. Questions and discussion related to MOHID Land
epelde.ane@gmail.com
MOHID Advanced user
Posts: 172
Joined: Thu Jan 01, 1970 00:00

Slow running

Postby epelde.ane@gmail.com » Fri Oct 21, 2011 09:19

Hi again!

I´m running two simulations with homogeneous soil and without vegetation. One of them without evapotranspiration and the other with it. The simulation period is 1 year and I think it last too much for the characteristics I´m taking into account. The thing is that I don´t know what can I change or what things should be changed in order to improve this.
The drainage network is composed of 594 nodes, and in the model output window I can see that the average time step is 142 seconds and the "Seconds per Iteration : 0.2134s"
Does this seem ok?

How does afect the processing time and data "writing" time the options I have in the different modules? Is there any guide/book I check to have a better understanding about it?

Thanks!!
ane

Jauch
Site Admin
Posts: 98
Joined: Thu Jan 01, 1970 00:00

Re: Slow running

Postby Jauch » Fri Oct 21, 2011 11:20

Hi Ane :)

There are a lot of things that will have impact in the processing time of a simulation.
The main ones that I can remember right now are:

1. Rain/Irrigation: More rain/irrigation and/or more rain/irrigation duration, more time needed
2. Number of cells in the domain: more cells, more time needed.
3. Height of cells: more thin cells are, more time needed
4. Drainage network: More detailed drainage network, more time needed

If you have water on channel all the time, this will slow down your average time step and the simulation will take longer to finish.

The "tolerances" used, like the THETA_TOLERANCE in the PorousMedia input data file, will have impact too. So, lower values will make the run slower, but will give, probably, best results. Depending on the cell size and basin size, you can try to increase a bit (a order of magnitude, for example). This can speed up the run.

If you're using variable DT (VARIABLEDT), a greater MAXDT eventually can help to speed up the running. I usually uses 3600 seconds but you can try higher values.
But all of this will have impact on the results, so you need to observe if the impact is sufficient low that you can live with it :)

The values you show about the seconds per iteration are not the best I alread see, but seens ok to me. One simulation that just finish right now had an Average Time Step of 120 seconds.

Jauch
Site Admin
Posts: 98
Joined: Thu Jan 01, 1970 00:00

Re: Slow running

Postby Jauch » Fri Oct 21, 2011 11:24

About the "wrinting" of data to files...
If you increase the buffer, this will mean fewer writing events and usually this can improve a little the run performance, but unless you're writing to a folder on a network drive, I think the impact will not be that much.

On the other hand, if you are writing data at small intervals (I usually uses hour or daily intervals for information), this can lead to a penalty in the performance, because files will growth larger and take time to write to them, mainly the HDF's...

epelde.ane@gmail.com
MOHID Advanced user
Posts: 172
Joined: Thu Jan 01, 1970 00:00

Re: Slow running

Postby epelde.ane@gmail.com » Mon Nov 28, 2011 16:44

Hello!
I know that in mohid studio there is an option to see which is the parameter that is slowing the time step. Is somewhere in "Schedule" but I cant find where it is.
Anyone can help me please?

Jauch
Site Admin
Posts: 98
Joined: Thu Jan 01, 1970 00:00

Re: Slow running

Postby Jauch » Tue Nov 29, 2011 18:45

Hi Ane :-)

According to David, you can use this option on the Schedule of Mohid Studio:
Log CPU Time

This option will create a log of the time spent to compute each most important task in the model.
Also, this will slower the model due to the overhead of file write and time compute...
So, I advise to use only to find wich task is most timing consuming to see if its possible to do something to speed up the model :-)


Return to “MOHID Land”

Who is online

Users browsing this forum: No registered users and 1 guest