Exec Intervals for solver activation

[suecook]

Hello,

I've been trying to use Exec Intervals to switch off a solver for the first timestep in a simulation.

In the Simulation section I use:
Timestep Intervals(2) = 1 2
Timestep Sizes(2) = 0.005 0.005

And then in the Solver:
Exec Solver = "After TimeStep"
Exec Intervals (2) = 100 1

But the solver still runs on all timesteps.

If I try "Exec Intervals (2) = 1 100" then the solver runs as I expected for only the first timestep, then switches off for the rest of the simulation.

If I try using "Exec Intervals (2) = 0 1" then I get an error message: "18453 Floating point exceptionElmerSolver"

I'm now a bit confused about how Exec Intervals works. Does anyone have any ideas of what input I should be using?

Thanks,

Sue

[mzenker]

Hi,

I found the question interesting and had a short look into the source code. In MainUtils.src, there is the following section:

Code: Select all

     ExecIntervals => ListGetIntegerArray( Params,'Exec Intervals', Found )
     IF( .NOT. Found ) THEN
       ExecIntervals =>  ListGetIntegerArray( Params,'Exec Interval', Found )
     END IF
     IF ( Found ) THEN
       TimeVar => VariableGet( Model % Variables, 'Timestep Interval' )
       timei = NINT(Timevar % Values(1))

       TimeVar => VariableGet( Model % Variables, 'Timestep' )
       timestep = NINT(TimeVar % Values(1))

       IF( MOD( timestep-1, ExecIntervals(timei)) /= 0 ) RETURN
     END IF

So a zero value for Exec Intervals leads to an error because of the MOD.
And if I understand correctly, the solver is always executed at the first timestep. Why this has been implemented that way, I don't know...

HTH,

Matthias

[raback]

Hi

There is clearly room for improvement.

First of all, the case "0" should be treated separately as it is now for "Output Intervals".

Also there could be "Exec Intervals Offset" so that one could choose the first active step. Currently it is zero. This would enable also various staggered schemes.

I tentatively implemented that but unfortunately the svn is under migration so I cannot commit it just now. I hope sf.net will get Elmer code there soon...

If you compile yourself you could add something like:

Code: Select all

      
IF( ExecIntervals(timei) == 0 ) RETURN

-Peter

[suecook]

Hi Peter,

I made the change you suggested to MainUtils.src and now it's working exactly as I'd hoped.

Thank you for your help!

Sue