[gdal-dev] ReadAsArray

[Rutger]

Even Rouault-2 wrote
> Yuta,
> 
> Increasing GDAL_CACHEMAX might accelerate in case of repeated reads on
> windows 
> that are identical or overlapping already read windows. Or if the way you
> read 
> the raster doesn't follow its block shape : for example if the raster is 
> organized by lines/strips and you read by square blocks, or the reverse 
> situation.
> 
> GDAL_SWATH_SIZE is only used by CreateCopy().
> 
> Even

Interesting, thanks for mentioning this. The case you mention might seem
like bad practice, but it still true that VRT's only allow blocks of 128x128
right? VRT's are something i use all the time. And for example, Landsat
geotiff's from the USGS are delivered as stripes of '1 by width'. If
performance is really an issue i sometimes deliberately read chucks of '128
x width' in order to avoid the inefficiency. I'll try to see if increasing
the CACHE_MAX might do this 'on the fly' without me having to worry about
the alignment of the block definitions. 

Regards,
Rutger



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