"Duncan Murdoch" <murdoch.dun...@gmail.com> wrote in message news:4e259600.5070...@gmail.com... > On 11-07-19 7:48 AM, Matthew Dowle wrote: >> >> "Prof Brian Ripley"<rip...@stats.ox.ac.uk> wrote in message >> news:alpine.lfd.2.02.1107190640280.28...@gannet.stats.ox.ac.uk... >>> On Mon, 18 Jul 2011, Alireza Mahani wrote: >>> >>>> Simon, >>>> >>>> Thank you for elaborating on the limitations of R in handling float >>>> types. I >>>> think I'm pretty much there with you. >>>> >>>> As for the insufficiency of single-precision math (and hence >>>> limitations >>>> of >>>> GPU), my personal take so far has been that double-precision becomes >>>> crucial >>>> when some sort of error accumulation occurs. For example, in >>>> differential >>>> equations where boundary values are integrated to arrive at interior >>>> values, >>>> etc. On the other hand, in my personal line of work (Hierarchical >>>> Bayesian >>>> models for quantitative marketing), we have so much inherent >>>> uncertainty >>>> and >>>> noise at so many levels in the problem (and no significant error >>>> accumulation sources) that single vs double precision issue is often >>>> inconsequential for us. So I think it really depends on the field as >>>> well >>>> as >>>> the nature of the problem. >>> >>> The main reason to use only double precision in R was that on modern >>> CPUs >>> double precision calculations are as fast as single-precision ones, and >>> with 64-bit CPUs they are a single access. >>> So the extra precision comes more-or-less for free. >> >> But, isn't it much more of the 'less free' when large data sets are >> considered? If a double matrix takes 3GB, it's 1.5GB in single. >> That might alleviate the dreaded out-of-memory error for some >> users in some circumstances. On 64bit, 50GB reduces to 25GB >> and that might make the difference between getting >> something done, or not. If single were appropriate, of course. >> For GPU too, i/o often dominates iiuc. >> >> For space reasons, is there any possibility of R supporting single >> precision (and single bit logical to reduce memory for logicals by >> 32 times)? I guess there might be complaints from users using >> single inappropriately (or worse, not realising we have an instable >> result due to single). > > You can do any of this using external pointers now. That will remind you > that every single function to operate on such objects needs to be > rewritten. > > It's a huge amount of work, benefiting very few people. I don't think > anyone in R Core will do it. > > Duncan Murdoch
I've been informed off list about the 'bit' package, which seems great and answers my parenthetic complaint (at least). http://cran.r-project.org/web/packages/bit/index.html Matthew ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
