[Nexus-developers] NXmakedata with unlimited size - chunking question

[Zikovsky, Janik L.]

That solves my problem perfectly - thanks a lot Freddie!

Cheers,

Janik Zikovsky
Scientific Data Analysis Group, Spallation Neutron Source

________________________________________
From: nexus-developers-bounces at nexusformat.org [nexus-developers-bounces at nexusformat.org] On Behalf Of freddie.akeroyd at stfc.ac.uk [freddie.akeroyd at stfc.ac.uk]
Sent: Wednesday, August 10, 2011 12:01 PM
To: nexus-developers at nexusformat.org
Subject: Re: [Nexus-developers] NXmakedata with unlimited size -        chunking        question

Janik,

There is no way to specify the chunk size with NXmakedata() - instead you need to use NXcompmakedata() specifying the chunk size in the "bufsize" parameter and, if you do not actually want to have compression, giving NX_COMP_NONE as the compression type

Regards,

Freddie

> -----Original Message-----
> From: nexus-developers-bounces at nexusformat.org [mailto:nexus-
> developers-bounces at nexusformat.org] On Behalf Of Zikovsky, Janik L.
> Sent: 10 August 2011 16:36
> To: nexus-developers at nexusformat.org
> Subject: [Nexus-developers] NXmakedata with unlimited size - chunking
> question
>
> Hello all,
>
> I have been calling NXmakedata() with the first dimension set to
> NX_UNLIMITED so as to allow extendible arrays; this is when writing to
> HDF5 files. This works, but from what I can tell by using hdfview, the
> data sets created use a chunk size of 1 in the first dimension.
>
> This small chunk size increases writing time by approximately one
> thousand (!) times in my application. Does anyone know how to set the
> chunk size when calling NXmakedata()?
>
> Thanks!
>
> Janik Zikovsky
> Scientific Data Analysis Group, Spallation Neutron Source
>
>
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