[petsc-users] Unable to create >4GB sized HDF5 files on Cray XC30

[Jed Brown]

Juha Jäykkä <juhaj at iki.fi> writes:

> I'll leave the parameter for others to implement: I don't have a good idea of 
> how to do that. I believe I can provide a testing environment (but no access 
> to it, I'm afraid) for those big files, just let me know what kind of test 
> suite I should create. Not that the old chunking seems to have had much 
> testing considering how seriously broken it is. ;)

Yes, but we like to improve test coverage when we make changes.  The new
code is more lines doing more complicated (hopefully less wrong) things,
so it ought to be tested.  The parameter could be controlled by:

PetscViewerHDF5SetMaxChunkSize(PetscViewer viewer,size_t max_chunk);

>> > +  // just in case some libraries do not empty memory for local variables:
>> We have to use C89-style comments because of Microsoft.
>
> What is this, Microsoft's compiler cannot do C99? Is it too new a standard, at 
> 14 years old?

Sadly, Microsoft does not intend to ever implement C99.

http://blog.reverberate.org/2012/03/microsoft-please-support-at-least-tiny.html

That said, I personally would not have a problem with using those C99
features that Microsoft's C++ compiler supports.  That even includes
variadic macros (well, a bastardized version, because when they
"cherry-picked" it from C99, they implemented the semantics wrong,
though that mistake is only triggered in peculiar cases).

But unless PETSc as a whole make a decision to allow C99 features, we
have to stick to C89.  (Public headers should use C89 syntax forever
because we don't want to impose a dialect on users.)

>> > +
>> > +  // some requirements for the chunks (assuming no split along time-step)
>> > +  int ranks;
>> Declarations cannot be mixed with statements in C89.
>
> Microsoft again? I've reverted these *standard* pieces of code into an 
> obsolete, old standard. I really had no idea there are STILL compilers around 
> which cannot do C99.

Shocking, I know.  If only they didn't have so much market share...
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