On Wed, 3 Dec 2003, Tim Jenness wrote:
> SCUBA-2 will potentially be creating images > 2GB in size. We are
> intending to use NDF for this but I remember at one of the programmer's
> meetings I attended that this largefile support required some fixes to HDS
> that Brian was looking into.
>
> Did those fixes ever make it into HDS? If not, how easy is it for this
> support to be added? Switching from NDF to FITS is not an option unless
> kappa and ccdpack switch to FITS since we were intending to use Starlink
> apps in the pipeline.
Hi Tim,
here's what I remember about the status of moving large file support.
Brian's changes to HDS have never made it out of RAL, so only he can let
us know what state that work is in (the issue was to do with the size of
the pointers stored in an HDS file, these limit offsets within an HDS file
to around 500Mb, with your full featured NDFs I expect you'd run into this
problem quite quickly). But, once that was released and proved to work,
the applications themselves will need work too, as they store addresses in
Fortran integers, which are 32 bit. We developed a system to work around
this (see CNF_PVAL), which Mark looked at using in an automated fixup
script, but all that worked has been stalled for quite some time.
Mark produced a document about his work, but I've lost the reference to
that.
Cheers,
Peter.
(ps, clearly moving to FITS would not help much here as we'd still have
the Fortran memory mapping problem to contend with).
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