From: Prof Brian Ripley > > On Fri, 27 Aug 2010, peter dalgaard wrote: > > > > > On Aug 27, 2010, at 2:44 PM, Liaw, Andy wrote: > > > >> I'd very much appreciate guidance on this. A user > reported that the > >> as.double() coercion used inside the .C() call for a function in my > >> package (specifically, randomForest:::predict.randomForest()) is > >> taking up significant amount of time when called repeatedly, and > >> Removing some of these reduced run time by 30-40% in some cases. > >> These arguments are components of the fitted model (thus do not > >> change), and are matrices. Some basic tests show no difference in > >> The result when the coercions are removed (other than > faster run time). > >> What I like to know is whether this is safe to do, or is > it likely to > >> lead > >> to trouble in the future? > > > > In a word: yes. It is safe as long as you are absolutely sure that > > the argument has the right mode. The unsafeness comes in > when people > > might unwittingly use, say, an integer vector where a double was > > expected, causing memory overruns and general mayhem. > > > > Notice, BTW, that if you switch to .Call or .External, then > you have > > much more scope for handling such details on the C-side. E.g. you > > could coerce only if the object has the wrong mode, avoid > > duplicating things you won't be modifying anyway, etc. > > But as as.double is effectively .Call it has the same freedom, and it > does nothing if no coercion is required. The crunch here is > likely to > be > > ‘as.double’ attempts to coerce its argument to be of > double type: > like ‘as.vector’ it strips attributes including names. > (To ensure > that an object is of double type without stripping > attributes, use > ‘storage.mode’.) > > I suspect the issue is the copying to remove attributes, in which case
I can certainly believe this. I've tried replacing as.double() to c(), thinking attributes need to be stripped. That actually increased run time very slightly instead of reducing it. > storage.mode(x) <- "double" > > should be a null op and so both fast and safe. Will follow this advise. Thanks to both of you for the help! Best, Andy > -- > Brian D. Ripley, rip...@stats.ox.ac.uk > Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/ > University of Oxford, Tel: +44 1865 272861 (self) > 1 South Parks Road, +44 1865 272866 (PA) > Oxford OX1 3TG, UK Fax: +44 1865 272595 > Notice: This e-mail message, together with any attachments, contains information of Merck & Co., Inc. (One Merck Drive, Whitehouse Station, New Jersey, USA 08889), and/or its affiliates Direct contact information for affiliates is available at http://www.merck.com/contact/contacts.html) that may be confidential, proprietary copyrighted and/or legally privileged. It is intended solely for the use of the individual or entity named on this message. If you are not the intended recipient, and have received this message in error, please notify us immediately by reply e-mail and then delete it from your system. ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
