Why are r.patch'ed files so slooowwww?

[Simon Cox]

I have a bunch of not-large rasters (240rx360c) which tile together to
cover a much larger area.  I thought it would be useful to use r.patch to
stitch these together so I could subset it just using g.region, etc.
However, when I d.rast the resultant file it is soooo slooowwww it is not
funny.  I can display _all_ the tiles in a much much much shorter time.
What is the story here?  any ideas?

(I have tried 9-at-a-time, 4-at-a-time, 2-at-a-time, always being careful
to set the region to exactly cover the contiguous area only, but horrible
performance in all cases.)

Thanks for your suggestions.            Simon Cox

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Dr Simon Cox                          __  \
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