It is more efficient to write
let {p in PROD, t in 1..T} x[p,t] := y[p,t];
than
for {p in PROD}
for {t in 1..T}
let x[p,t] := y[p,t];
and in general indexed "let" statements are more efficient than nested "for"
statements. The difference in efficiency becomes substantial when the inner
assignment statement is executed many times (say, tens or hundreds of
thousands).
Bob Fourer
4er@...
> -----Original Message-----
> From:
ampl@... [mailto:
ampl@...]
> On Behalf Of Yasin053
> Sent: Wednesday, August 19, 2009 2:18 PM
> To:
ampl@...
> Subject: [AMPL 2776] Re: changing the values of a vector without loop
>
>
> Is the below line computationally more efficient(i.e., does it reduce CPU
> time)?
>
> Robert Fourer-2 wrote:
> >
> > There is no assignment statement exactly of this kind in AMPL. But you
> > should use an indexed assignment statement rather than a "for" loop; for
> > example:
> >
> > let {p in PROD, t in 1..T} x[p,t] := y[p,t];
> >
> >
> >> -----Original Message-----
> >> From:
ampl@... [mailto:
ampl@...]
> >> On Behalf Of Yasin053 [
yasin053@...]
> >> Sent: Monday, August 17, 2009 2:35 AM
> >> To:
ampl@...
> >> Subject: [AMPL 2766] changing the values of a vector without loop
> >>
> >> Hi,
> >> I would like to know if I can set the values of a vector x to those of
> >> a vector y without using a loop. In Java or C, this can be done with a
> >> single
> >> line: x=y.
> >> Thank you,
> >>
> >
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