[gdal-dev] Help with idiomatic GDAL solution for raster algebra benchmark

[Even Rouault]

> I ended up with the following timings:
> 
> GDAL-Only using ReadBlock(...)                         :   7.7 seconds
> GDAL-Only using RasterIO(...)                            : 30.1 seconds
> GDAL-Only using GetLockedBlockRef(...)         :   8.9 seconds
> Pronto Raster using GetLockedBlockRef(...)     : 10.6 seconds
> 
> I suppose the relatively poor performance of RasterIO is known 
> (https://lists.osgeo.org/pipermail/gdal-dev/2008-March/016357.html and 
> https://trac.osgeo.org/gdal/ticket/2266), although I don't understand 
> the reason for it.

The main reason is that RasterIO() involves an extra memcpy() from the block 
cache buffer to the user provided buffer.

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