Re: [h5md-user] Dataset layouts

[Peter Colberg]

Hi Pierre,

On Tue, Jun 09, 2015 at 10:30:31PM +0200, Pierre de Buyl wrote:
> I understand the motivation. Did you notice a difference in performance or is
> there some other motivation?

It is not related to performance at all.

Non-compact and compact datasets have to be handled differently for
writing and reading. A non-compact dataset is only written/read by one
process, while a compact dataset is written/read by all processes. 

When writing/reading a compact dataset from only one process, the
program will hang. When writing a non-compact dataset from all
processes, the program will block for a finite period due to
write conflicts.

The compact layout is preferable over the non-compact layout for
efficiency reasons (and being equivalent to attributes), hence I
propose to mandate the compact layout.

Peter