Re: reduction funs optimizations + min/max question

[Jaroslav Hajek]

On Mon, Feb 16, 2009 at 8:10 PM, Søren Hauberg <address@hidden> wrote:
> man, 16 02 2009 kl. 09:23 +0100, skrev Jaroslav Hajek:
>> On Fri, Feb 13, 2009 at 9:22 PM, Jaroslav Hajek <address@hidden> wrote:
>> > hi,
>> >
>> > this changeset: http://hg.savannah.gnu.org/hgweb/octave/rev/53b4fdeacc2e
>> > reimplements the reduction and cumulative reduction "cores" sum, prod,
>> > sumsq, cumsum and cumprod
>> > for better performance.
>> >
>>
>>
>> Following similar ideas, I optimized also min/max reductions and
>> any/all.
>
> Some time back there was a request for 'cummin' and 'cummax' (cumulative
> min and max), but it wasn't trivial to implement. Is it easier to
> implement such functions with your recent changes?
>
> Søren

Well, it would take some work, but seems relatively straightforward.
We'd need to settle on a specification, though.
So, my idea:
y = cummax (x, dim);
returns cumulative maximum along dimension dim. If dim is omitted,
operates along the first non-singleton dimension.
[y, i] = cummax (x);
returns also cumulative maximum indices.
cummin is analogical.

So, the question is: Is it worth doing this for 3.2?

It seems to me that this function cannot be reasonably simulated in
m-code without using a loop or sacrificing the O(N) complexity. Can
anyone elaborate on expected usage?

cheers

-- 
RNDr. Jaroslav Hajek
computing expert
Aeronautical Research and Test Institute (VZLU)
Prague, Czech Republic
url: www.highegg.matfyz.cz