[GRASS-dev] v.what.rast speedup - was Re: r.random: now with optional cover map parameter

[Markus Neteler]

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];
>         else
>             cache[i].count++;
>     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
in v.what.rast...

Markus
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