Without the special code the performance can be improved slightly (in this
case):
ts 'c}b,:a'
0.01927602 41945088
ts' a+c*b-a'
0.016176513 25167616
(c}b,:a)-:a+c*b-a
1
R.E. Boss
> -----Oorspronkelijk bericht-----
> Van: programming-boun...@jsoftware.com [mailto:programming-
> boun...@jsoftware.com] Namens Ric Sherlock
> Verzonden: woensdag 21 december 2011 20:21
> Aan: Programming forum
> Onderwerp: Re: [Jprogramming] choosing between alternates (iif, ifelse)
>
> On Thu, Dec 22, 2011 at 5:54 AM, Henry Rich <henryhr...@nc.rr.com>
> wrote:
> > Note that
> >
> > c}b,:a
> >
> > does indeed compute b,:a. But if it's used in the precise form
> >
> > result =: c}b,:a
> >
> > the computation is avoided.
> >
> > b =: 1e6$4
> > a =: 1e6$4
> > c=: ? 1e6$ 2
> > ts 'c}b,:a'
> > 0.0401299 2.09725e7
> > ts 'q =: c}b,:a'
> > 0.0112949 4.19558e6
> >
> > There are other special cases; see the Special Code page.
>
> Especially the "in-place" case where items of b or a are altered in-place.
> Note that timespacex is defined in the stdlib in J7.
>
> timespacex ' c}b,:a'
> 0.0229656 4.19451e7
> timespacex 'q=: c}b,:a'
> 0.00915218 8.39091e6
> timespacex 'b=: c}b,:a'
> 0.00612322 2304
> timespacex 'b=: c}b,:a'
> 0.00612322 2304
> timespacex 'b=: c}a,:b'
> 0.00615121 2304
> timespacex 'a=: c}b,:a'
> 0.00612789 2304
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