[aspect-devel] [cse.ucdavis.edu #13562] Fwd: Fwd: error when writing checkpoint files

[Wolfgang Bangerth]

On 07/07/2018 06:45 AM, Magali Billen wrote:
> I’ll be at CIDER the last two weeks of  July and I’ll try to talk to Rene in person about this issue and try to understand
> more about what options might exists.  Since this is all handled by other libraries (p4est), there may be no real option.   I
>   don’t feel like I have the expertise or experience with Aspect to wade into this on my own. Maybe after talking with Rene,
> we can see about trying to compiling p4est with mpi-io and see what happens.

p4est can be configured to disable MPI-IO. So that's a problem that can be 
solved. But deal.II also uses MPI-IO, here:

https://github.com/dealii/dealii/blob/master/source/base/data_out_base.cc#L7286

This deal.II function is called from essentially all ASPECT runs:

https://github.com/geodynamics/aspect/blob/master/source/postprocess/visualization.cc#L594

The default for the number of grouped files is 16, and I suspect that most 
people leave it as is -- so basically everyone ends up in the `else` branch in 
line 598.

In other words, while I don't know whether people use checkpoint/restart 
frequently, pretty much everyone I know uses VTU output, and that uses MPI-IO. 
I can't really reconcile this, but it seems to suggest that MPI-IO must work 
for most of our users.

Best
  Wolfgang


-- 
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Wolfgang Bangerth          email:                 bangerth at colostate.edu
                            www: http://www.math.colostate.edu/~bangerth/