[Rcpp-devel] R vectorisation vs. C++ vectorisation

[Martyn Plummer]

I believe that such a function is normally called "clamp".
Martyn

Quoting Romain Francois <romain at r-enthusiasts.com>:

> clip it is, with this order:
>
> p = clip( 0.0, p, 1.0 ) ;
>
> which I found more natural.
>
> For now, I implemented only a version with primitives for the first and
> last argument and sugar expression for the one in the middle, but we can
> imagine writing vector versions everywhere.
>
> Romain
>
> Le 21/11/12 14:22, Alexandre Bujard a écrit :
> > How about clip():
> >      p = clip(p, 0.0, 1.0);
> >
> > Great idea!!!
> >
> >
> > On Wed, Nov 21, 2012 at 2:00 PM, Romain Francois
> > <romain at r-enthusiasts.com <mailto:romain at r-enthusiasts.com>> wrote:
> >
> >     Le 21/11/12 13:22, Darren Cook a écrit :
> >
> >         I wrote:
> >
> >                     P.S. I don't think the sugar versions can be made
> >                     any quicker, because
> >                     they have to allocate intermediate vectors, and do
> >                     more memory copies.
> >
> >
> >         By "sugar versions" I meant vacc4() vs. vacc3()
> >         (https://gist.github.com/__4111256
> >         <https://gist.github.com/4111256>) not pmin() and friends. The
> >         vacc4()
> >         code looks like:
> >
> >             NumericVector p(age.size());
> >             p = 0.25 + 0.3 * 1 / (1 - exp(0.04 * age)) + 0.1 * ily;
> >             p = p * ifelse(female, 1.25, 0.75);
> >             p = pmax(0,p);
> >             p = pmin(1,p);
> >
> >         Each operation copies the whole NumericVector each time, each of
> >         which
> >         needs a memory allocation.
> >
> >
> >     Nope. The NumericVector::operator=( sugar expression ) is used and
> >     memory for p is allocated just once, when p is constructed with this
> >     lne:
> >
> >       NumericVector p(age.size());
> >
> >     None of the "p = ..." lines allocate memory for p.
> >
> >     The differences in timing don't come from additional memory
> allocations.
> >
> >     Although this thread allows me to identify something that can be
> >     improved in the operator=.
> >
> >
> >         vacc3a() does the same pipeline of operations on a single
> >         double, which
> >         is therefore likely to be a single CPU register, and the whole of
> >         vacc3a() will be inlined in vacc3().
> >
> >
> >             Also, I'm probably goinf to add a function that does the
> >             equivalent of :
> >
> >             pmax( b, pmin( a, x ) )
> >
> >             I'm thinking of naming it pminmax. Any better idea ?
> >
> >
> >         I'd expect a function called minmax() to return two values, the
> >         min and
> >         max function. The "p" prefix is too subtle for me :-)
> >
> >         How about clip():
> >              p = clip(p, 0.0, 1.0);
> >
> >
> >
> >     I like "clip".
> >
> >
> >
> >         This is such a common operation that I'm surprised R doesn't
> already
> >         have a function like this!
> >
> >         Darren
> >
> >
> >
> >
> >     --
> >     Romain Francois
> >     Professional R Enthusiast
> >     +33(0) 6 28 91 30 30 <tel:%2B33%280%29%206%2028%2091%2030%2030>
> >
> >     R Graph Gallery: http://gallery.r-enthusiasts.__com
> >     <http://gallery.r-enthusiasts.com>
> >     `- http://bit.ly/SweN1Z : SuperStorm Sandy
> >
> >     blog: http://romainfrancois.blog.__free.fr
> >     <http://romainfrancois.blog.free.fr>
> >     |- http://bit.ly/RE6sYH : OOP with Rcpp modules
> >     `- http://bit.ly/Thw7IK : Rcpp modules more flexible
> >
> >     _________________________________________________
> >     Rcpp-devel mailing list
> >     Rcpp-devel at lists.r-forge.r-__project.org
> >     <mailto:Rcpp-devel at lists.r-forge.r-project.org>
> >
> https://lists.r-forge.r-__project.org/cgi-bin/mailman/__listinfo/rcpp-devel
> >
> <https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel>
> >
> >
>
>
> --
> Romain Francois
> Professional R Enthusiast
> +33(0) 6 28 91 30 30
>
> R Graph Gallery: http://gallery.r-enthusiasts.com
> `- http://bit.ly/SweN1Z : SuperStorm Sandy
>
> blog:            http://romainfrancois.blog.free.fr
> |- http://bit.ly/RE6sYH : OOP with Rcpp modules
> `- http://bit.ly/Thw7IK : Rcpp modules more flexible
>
> _______________________________________________
> Rcpp-devel mailing list
> Rcpp-devel at lists.r-forge.r-project.org
> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
>



-----------------------------------------------------------------------
This message and its attachments are strictly confidential. If you are
not the intended recipient of this message, please immediately notify 
the sender and delete it. Since its integrity cannot be guaranteed, 
its content cannot involve the sender's responsibility. Any misuse, 
any disclosure or publication of its content, either whole or partial, 
is prohibited, exception made of formally approved use
-----------------------------------------------------------------------