[GRASS-dev] r3.stats and heapsort

[Sören Gebbert]

Hi Hamish,

Hamish schrieb:
> Congratulations on the new module.
> 
> Sören Gebbert wrote:
>> Because of the quadratic complexity for subrange calculations, the
>> number of subranges is limited to 1 - 100000.
> 
> It is much better to add a warning in that case that the operation will
> take some time, or let the G_alloc() fns do their job and report a
> memory error (preferably right at the start of the run).

I agree.

> 
> Some folks using GRASS will have access to supercomputers or big servers
> with 28+GB RAM, we shouldn't artificially put limits on them because we
> don't have that hardware ourselves. Or maybe it is common to have 16GB
> 64bit motherboards in the next few years, then we have to revisit the
> code to let that be used.

I think the RAM is not the limiting factor, the quadratic complexity
bothers me. I need to figure out what Michael Shapiro had in mind, when 
he coded r.stats ... for me it was easier to code it by myself and
invent the weel again, then understanding the code of r.stats.

Well, i have a binary tree search for subranges in mind and
r3.stats is still in an early development state. So there are
still a lot of things i can try out to reduce the memory usage and
the needed CPU cycles. :)

Soeren

> 
> 
> Hamish
> 
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