In the case of updating lots of small arrays, there is
little difference between the 2. But this version is
also a small improvement. Though upfltr2 turns up to
be a bit faster.
I asked the question, because I wondered if this was
the "right" way to do this common task. I guess all
of these are fast enough.
upfltr5 =: 4 : 0
NB. update filtered y. x upV`fltrV,
'`up f' =. x
(up (f y)#y) (I. f y)}y
)
zz=. 1e4 10 $?.2e2# 20
6!:2 'zz=:+:`(10&>) upfltr"1 zz'
0.218465754726
6!:2 'zz=:+:`(10&>) upfltr4"1 zz'
0.213576865216
6!:2 'zz=:+:`(10&>) upfltr5"1 zz'
0.208311670897
6!:2 'zz=:+:`(10&>) upfltr2"1 zz'
0.195342704171
--- Devon McCormick <[EMAIL PROTECTED]> wrote:
> May be slightly better to use a temporary instead of
> repeating "f y" (see
> "upfltr4" below):
>
> upfltr2=: 4 : 0
> NB. update filtered y. x updateV`fltrV,
> '`up f' =. x
> (f y)}y,:up y
> )
>
> zz=. 1e4?1e9
> 6!:2 '+:`(10&>) upfltr2 zz'
> 0.0019156066 NB. Not as fast...
> 6!:2 '+:`(10&>) upfltr zz'
> 0.00057269849
>
> upfltr3=: 4 : 0
> NB. update filtered y. x updateV`fltrV,
> '`up f' =. x
> (up y#~f y) (I. f y) } y
> )
> +:`(10&>) upfltr3 5 9 11 12
> 10 18 11 12
> 6!:2 '+:`(10&>) upfltr3 zz'
> 0.00056320007 NB. Basically the
> same...
>
> upfltr4=: 4 : 0
> NB. update filtered y. x updateV`fltrV,
> '`up f' =. x
> xx=. f y
> (up xx#y) (I. xx)}y
> )
> 6!:2 '+:`(10&>) upfltr4 zz'
> 0.00045368895 NB. Marginally faster?
> Hard to conclude...
>
>
> On 4/19/06, Pascal Jasmin <[EMAIL PROTECTED]>
> wrote:
> >
> > NB. update only selected items from y with
> monad
> > function of y, leave rest unchanged.
> > upfltr =: 4 : 0
> > NB. update filtered y. x updateV`fltrV,
> > '`up f' =. x
> > (up (I. f y){ y) (I. f y) } y
> > )
> > NB. double items greater than 10:
> > +:`(10&>) upfltr 5 9 11 12
> > 10 18 11 12
> >
> > is there a faster way to implement the above?
> Seems
> > to me the above verb should be one of the built-in
> > gerund ammend options, (maybe it is, and I just
> don't
> > understand the documentation for it).
> >
> ...
> --
> Devon McCormick
> ^me^ at acm.
> org is my
> preferred e-mail
>
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>
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