Re: [Opengrads-devel] errors on sdfopen with hdf

[Jennifer A. <jm...@co...>]

On Feb 6, 2008, at 1:09 PM, Arlindo da Silva wrote:

> On Feb 6, 2008 10:44 AM, Jennifer Adams <jm...@co...> wrote:
>
> Arlindo,
> I have put some print statments in gasdf.c to see why this is  
> happening.
> The HDF routine SDdiminfo returns the following information on
> model.hdf:
>
> dim_id,name,dimsize,dtype,ndatts = 327680 time 0 6 1
> dim_id,name,dimsize,dtype,ndatts = 327681 longitude 72 6 2
> dim_id,name,dimsize,dtype,ndatts = 327682 latitude 46 6 2
> dim_id,name,dimsize,dtype,ndatts = 327683 levels 7 6 5
>
> Looks like the file has a time dimension of size 0. I remember now
> that when I discovered this during development, I put in the
> following line:
>        if (dimsize==0) dimsize=1; /* would you have a coordinate  
> axis with
> size==0 */
>
> The interesting thing is that when I run ncdump (from the HDF4.2r2
> library build) it gives me this:
>
> dimensions:
>         time = UNLIMITED ; // (5 currently)
>         longitude = 72 ;
>         latitude = 46 ;
>         levels = 7 ;
>
> It is possible that this is a bug in the SD interface. Ncdump uses  
> the "NC" interface which is sometimes a more basic, low level  
> interface than SD.  (I say "sometimes" because the hdf-4 is not so  
> cleanly layered). I suspect that your ctl/"DTYPE hdf" interface  
> will have similar problems, correct?
The 'dtype hdfsds' works fine because the required TDEF metadata is  
provided in the descriptor file -- is doesn't need to use SDdiminfo  
to discover the size of the time axis.

> The file "model.hdf" was written with the "NC" interface through  
> LATS. Leading to this version of hdf-4, I reported a couple of bugs  
> to THG in the hrepack utility which  did not work properly with HDF  
> files written by the "NC" interface (all GMAO files are written  
> that way, although LATS is not involved).  It is very possible that  
> this is another one of those bugs.
>
> We have 2 options, report the bug to the THG (we will need a small  
> example demonstrating the problem), or try to dig in the hdf-4  
> sources and contribute a patch to them. They have usually being  
> very responsive to my bug reports. What do you prefer?

As I see it, there is a bug in the lats4d pathway that creates hdf  
files, not in the v2 code that reads them.

Jennifer