[JimKnopf]

Hi there!

Though I don't have a problem, recently I was wondering why there are two strategies to iterate in time.

First there is runTime.loop() which is used as a condition for a while loop.

Second there is runTime.run() as a condition for the while loop and runTime++ for iterating

Does this make sense? I don't get. Maybe someone can enlighten me.

greetz
Jim

[marupio]

Read src/OpenFOAM/db/Time/time.H, it has comments describing the difference. I think .loop increments runTime, whereas .run is only a test if the run should continue, but there may be some fine differences with function objects.

[user_of_cfx]

I am bringing this forward again and about to ask again... From Time.H (bold highlighting by me):

            //- Return true if run should continue,
            //  also invokes the functionObjectList::end() method
            //  when the time goes out of range
            //  \note
            //  For correct behaviour, the following style of time-loop
            //  is recommended:
            //  \code
            //      while (runTime.run())
            //      {
            //          runTime++;
            //          solve;
            //          runTime.write();
            //      }
            //  \endcode
            virtual bool run() const;

            //- Return true if run should continue and if so increment time
            //  also invokes the functionObjectList::end() method
            //  when the time goes out of range
            //  \note
            //  For correct behaviour, the following style of time-loop
            //  is recommended:
            //  \code
            //      while (runTime.loop())
            //      {
            //          solve;
            //          runTime.write();
            //      }
            //  \endcode
            virtual bool loop();

So it looks like both do the same thing in different ways. My question is, is there a rule to choose which runTime option to use with what solver? Initially I thought this may be something to differentiate timesteps from the corrector iterations inside the PIMPLE algorithm for example, but then obviously both could do this equally well. Any insight to this will be appreciated.

[hk318i]

Simply, run() gives the developer a chance to calculate whatever needed before updating the time index. On the other hand loop(), updates the time at the beginning of the loop.
You are absolutely right, based on these examples in this comment both are exactly the same but it is not always the case. I can recall one example, check rhoCentralFoam, you will find that run() is used because interpolation is required before solving the equations.

Best Regards,
Hassan Kassem

[user_of_cfx]

Originally Posted by hk318i

Simply, run() gives the developer a chance to calculate whatever needed before updating the time index. On the other hand loop(), updates the time at the beginning of the loop.
You are absolutely right, based on these examples in this comment both are exactly the same but it is not always the case. I can recall one example, check rhoCentralFoam, you will find that run() is used because interpolation is required before solving the equations.

Best Regards,
Hassan Kassem

I saw how it's used in rhoCentralFoam.. pretty cool. Cheers for the tip.