[gdal-dev] Re: Problems with large raster sizes (WMS/TMS)

Frank Warmerdam warmerdam at pobox.com
Fri Nov 13 11:05:11 EST 2009

Tamas Szekeres wrote:
> Hi Even,
> Yes, I thought it was a bit complicated issue. I would also support
> replacing the array of pointers with a hashtable to eliminate the
> unnecessary memory requirement. I've been looking at the code and
> found a hashset implementation in CPL which could probably be utilized
> here, however this one doesn't support to auto-grow and it should also
> store all the items with the same hash value (along with the key) in a
> linked list instead replacing each other. I don't think it would
> significantly slow down the lookup process since only the list of the
> same hash should be iterated.

Tamas / Even,

I would like any transition in this area to include some performance
analysis with large and modest sized images.

> The problem of the nRasterXSize limitation is more significant IMO,
> however I think it would be enough to change the type from integer to
> float or double and some type casts should be added in the related
> expressions. But it would indeed be a significant change in gdal,
> however I think we should start thinking about it in order to support
> the (virtually) large raster dimensions.

I would prefer to limit ourselves to 2 gigapixels by 2 gigapixels images
for the time being.  I just can't yet see that larger images are of
sufficient interest to justify the complexity involved in properly
supporting larger images throughout GDAL.

If we were to do so, I'd want it handled via an RFC.

Best regards,
I set the clouds in motion - turn up   | Frank Warmerdam, warmerdam at pobox.com
light and sound - activate the windows | http://pobox.com/~warmerdam
and watch the world go round - Rush    | Geospatial Programmer for Rent

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