[petsc-users] ISView() in PETSc 3.22

[Adrian Croucher]

hi Matt

On 2/10/24 1:01 am, Matthew Knepley wrote:
> On Mon, Sep 30, 2024 at 10:15 PM Adrian Croucher 
> <a.croucher at auckland.ac.nz> wrote:
>
>     hi, I am testing my (Fortran) code on PETSc 3.22 and have got it to
>     build. However I am getting some unusual new behaviour when I
>     write an
>     IS to an HDF5 file using ISView().
>
>     The attached minimal example shows the issue. It creates a simple
>     10-element IS and writes it to HDF5. With previous versions of PETSc
>     this would give me a 10x1 dataset containing the values 0 - 9, as
>     expected.
>
>     When I run it with PETSc 3.22 (in serial), I again get the expected
>     values written on stdout, so it looks like the IS itself is
>     correct. But
>     in the HDF5 file I get a 1x3 dataset containing the values (10,1,0).
>
>     Has something changed here?
>
>
> Yes. We now compress IS data sets by default. You can turn it off 
> using -is_view_compress 0. I am not sure
> what the best way to manage this is, but it makes a huge difference in 
> file size for checkpointing.

Thanks. I guess that's fine if it's being read back in by PETSc, but I 
have users with non-PETSc post-processing codes needing to read my 
output, and they aren't going to know what to do with these compressed 
datasets. I only write one IS at the start of each simulation, so it's a 
negligible contribution to the file size.

So I think I will need to disable the compression in my code. Is there a 
function call I can use to do that, to make sure it's always done 
without users needing to pass -is_view_compress 0?

- Adrian

-- 
Dr Adrian Croucher
Senior Research Fellow
Department of Engineering Science
Waipapa Taumata Rau / University of Auckland, New Zealand
email:a.croucher at auckland.ac.nz
tel: +64 (0)9 923 4611
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