Re: [boost] [accumulators]Couple notes

From: Gennadiy Rozental (gennadiy.rozental_at_[hidden])
Date: 2007-02-18 19:44:42

"Matthias Troyer" <troyer_at_[hidden]> wrote in message 
news:2F2BAA4A-9540-49EF-80F5-3E22D0A6B615_at_phys.ethz.ch...
>
> On 16 Feb 2007, at 19:47, Gennadiy Rozental wrote:
>
>>
>> "Matthias Troyer" <troyer_at_[hidden]> wrote in message
>> news:B503A931-963F-4F5B-8DCF-C6617D48EAAD_at_phys.ethz.ch...
>>>
>>> On 16 Feb 2007, at 19:24, Gennadiy Rozental wrote:
>>>
>>>>
>>>> Anyway.  IMO almost any solution would be good enough for me.
>>>> v.update()
>>>> would work either.
>>>
>>> Why is
>>>
>>> acc(v);
>>>
>>> a problem if
>>>
>>> v.update();
>>>
>>> is fine?
>>
>> I never said it's a problem. But from what understand it's completely
>> different thing. acc(0) would be more close to v  += 0; acc(v) is
>> more like
>> v *= 2;
>
> Now I'm really confused. acc is the accumulator, recording features
> like sum,min, max, mean, median, variance. In  what sense is acc(0)
> like v +=0 and acc(v) like v *= 2????

Umm. I maybe wrong.

Here is correct correspondence (<==> means equivalent):

accumulator_set<....> acc;
tracked_var<....> v;

acc(s1) ; <==> v = s1;
acc(s2) ; <==> v = s1;
acc(s3) ; <==> v = s3;

v+=s1 doesn't really have anything corresponding in current interface. Maybe 
something like this:

T value = 0;
accumulator_set<....> acc;
tracked_var<....> v;

value += s1;
v += s1; <==> acc(value);

value += s2;
v += s2; <==> acc(value);

value += s3;
v += s3; <==> acc(value);

value -= s4;
v -= s4; <==> acc(value);

value += 0;
v += 0; <==> acc(value);

If you think this as collecting samples of some variable values v+=0 look 
pretty natural. if you think about it as accumulating set of values 
acc(value) looks better.

Doesn't matter to me either way. It still does the same thing.

Gennadiy