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1.4 Checkpointing a FLUENT Simulation

The checkpointing feature of FLUENT allows you to save case and data files while your simulation is running. While similar to the autosave feature of FLUENT (Section  4.3.4), which allows you to save files throughout a simulation, checkpointing allows you slightly more control in that you can save a FLUENT job even after you have started the job and did not set the autosave option. Checkpointing also allows you to save case and data files and then exit out of FLUENT. This feature is especially useful when you need to stop a FLUENT job abruptly and save its data.

There are two different ways to checkpoint a FLUENT simulation, depending upon how the simulation has been started.

1.    FLUENT running under LSF or SGE

FLUENT is integrated with load management tools like LSF and SGE. These two tools allow you to checkpoint any job running under them. You can use the standard method provided by these tools to checkpoint the FLUENT job. For more information on using FLUENT and SGE or LSF, go to the documentation page on the Fluent Inc. User Services Center.

2.   Independently running FLUENT

When not using tools such as LSF or SGE, a different checkpointing mechanism can be used when running a FLUENT simulation. You can checkpoint a FLUENT simulation while iterating/time-stepping, so that FLUENT saves the case and data files and then continues the calculation, or so that FLUENT saves the case and data files and then exits.

  • Saving case and data files and continuing the calculation:

    On Linux/UNIX, create a file called check-fluent, i.e.,

        /tmp/check-fluent
    

    On Windows, create a file called check-fluent.txt, i.e.,

        c:\\temp\check-fluent.txt
    

  • Saving case and data files and exiting FLUENT:

    On Linux/UNIX, create a file called exit-fluent, i.e.,

        /tmp/exit-fluent
    

    On Windows, create a file called exit-fluent.txt, i.e.,

        c:\\temp\exit-fluent.txt
    

The saved case and data files will have the current iteration number appended to their file names.

FLUENT offers an alternate way to checkpoint an unsteady simulation. While the default behavior is to checkpoint the simulation at the end of the current iteration, for unsteady simulations you have the option of completing all of the iterations in the current time-step before checkpointing. This can be set by entering the following Scheme command prior to running the unsteady simulation:

(ckpt/time-step?#t)

Now when you save the checkpoint file (as described previously), the case and data file will be saved at the end of the current time-step and named accordingly. To switch back to the default checkpointing mechanism at the end of the current iteration, use the following Scheme command:

(ckpt/time-step?#f)

figure   

Note that the (ckpt/time-step?#t) command will have the effect only in the case of an unsteady simulation.

To change the default location of the saved case and data files, you can use the following Scheme commands:

(set! checkpoint/check-filename pathname)

and

(set! checkpoint/exit-filename pathname)

where pathname is the path you wish to set as the new default location of the saved case and data files.


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