[GRASS-dev] v.what.rast speedup - was Re: r.random: now with
optional cover map parameter
neteler at fbk.eu
Sun Oct 21 18:23:41 CEST 2007
Glynn Clements wrote:
> Hamish wrote:
>> Markus Neteler wrote:
>> > since v.what.rast is (for me) extremely slow, I have added
>> > cover map support to r.random.
>> > PS: v.what.rast still running on just 300k points while I
>> > implemented above :-) Anyone who could make v.what.rast faster?
>> Maybe it's the qsort(), maybe it's the i,j loop within a loop.
> The loop is certainly inefficient. Rather than shifting the entire
> array down every time it finds a duplicate, it should keep separate
> source and destination indices, e.g. (untested):
> for (i = j = 0; j < point_cnt; j++)
> if (cache[i].cat != cache[j].cat)
> cache[++i] = cache[j];
> point_cnt = i + 1;
> Glynn Clements <glynn at gclements.plus.com>
I am afraid to say that I don't know how to implement the suggestion
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