Hi Abby, I actually have a patch submitted that does this for unique/duplicated (only numeric cases I think) but it is, as patches from external contributors go, quite sizable which means it requires a correspondingly large amount of an R-core member's time and energy to vet and consider. It is in the queue, and so, I expect (/hope, provided I didn't make a mistake) it will be incorporated at some point. ( https://bugs.r-project.org/bugzilla/show_bug.cgi?id=17993)
You are correct that the speedups are quite significant for calling unique/duplicated on large vectors that know they are sorted: Speedup on my machine for a fairly sizable vector (length 1e7) ranges from about ~10x in the densely duplicated case up to ~60-70x in the sparsely duplicated case for duplicated(). For unique() it seems to range from ~10x in the densely duplicated case to ~15 in the spare case. I had thought that min and max already did this, but looking now, they don't seem to by default, thought ALTREP classes themselves do have an option of setting a min/max method, which would be hit. That does seem like low-hanging fruit, I agree, though in many cases the slow down from a single pass over the data to get a min probably isn't earthshattering. The others do seem like they could benefit as well. Best, ~G On Tue, Mar 16, 2021 at 2:54 PM Abby Spurdle <spurdl...@gmail.com> wrote: > There are some relatively obvious examples: > unique, which.min/which.max/etc, range/min/max, quantile, aggregate/split > > Also, many timeseries, graphics and spline functions are dependent on the > order. > > In the case of data.frame(s), a boolean flag would probably need to be > extended to allow for multiple column sorting, and > ascending/descending options. > > On Tue, Mar 16, 2021 at 11:08 AM Gabriel Becker <gabembec...@gmail.com> > wrote: > > > > Abby, > > > > Vectors do have an internal mechanism for knowing that they are sorted > via ALTREP (it was one of 2 core motivating features for 'smart vectors' > the other being knowledge about presence of NAs). > > > > Currently I don't think we expose it at the R level, though it is part > of the official C API. I don't know of any plans for this to change, but I > suppose it could. Plus for functions in R itself, we could even use it > without exposing it more widely. A number of functions, including sort > itself, already do this in fact, but more could. I'd be interested in > hearing which functions you think would particularly benefit from this. > > > > ~G > > > > On Mon, Mar 15, 2021 at 12:01 PM SOEIRO Thomas <thomas.soe...@ap-hm.fr> > wrote: > >> > >> Hi Abby, > >> > >> Thank you for your positive feedback. > >> > >> I agree for your general comment about sorting. > >> > >> For ave specifically, ordering may not help because the output must > maintain the order of the input (as ave returns only x and not the entiere > data.frame). > >> > >> Thanks, > >> > >> Thomas > >> ________________________________________ > >> De : Abby Spurdle <spurdl...@gmail.com> > >> Envoyé : lundi 15 mars 2021 10:22 > >> À : SOEIRO Thomas > >> Cc : r-devel@r-project.org > >> Objet : Re: [Rd] Potential improvements of ave? > >> > >> EMAIL EXTERNE - TRAITER AVEC PRÉCAUTION LIENS ET FICHIERS > >> > >> Hi Thomas, > >> > >> These are some great suggestions. > >> But I can't help but feel there's a much bigger problem here. > >> > >> Intuitively, the ave function could (or should) sort the data. > >> Then the indexing step becomes almost trivial, in terms of both time > >> and space complexity. > >> And the ave function is not the only example of where a problem > >> becomes much simpler, if the data is sorted. > >> > >> Historically, I've never found base R functions user-friendly for > >> aggregation purposes, or for sorting. > >> (At least, not by comparison to SQL). > >> > >> But that's not the main problem. > >> It would seem preferable to sort the data, only once. > >> (Rather than sorting it repeatedly, or not at all). > >> > >> Perhaps, objects such as vectors and data.frame(s) could have a > >> boolean attribute, to indicate if they're sorted. > >> Or functions such as ave could have a sorted argument. > >> In either case, if true, the function assumes the data is sorted and > >> applies a more efficient algorithm. > >> > >> > >> B. > >> > >> > >> On Sat, Mar 13, 2021 at 1:07 PM SOEIRO Thomas <thomas.soe...@ap-hm.fr> > wrote: > >> > > >> > Dear all, > >> > > >> > I have two questions/suggestions about ave, but I am not sure if it's > relevant for bug reports. > >> > > >> > > >> > > >> > 1) I have performance issues with ave in a case where I didn't expect > it. The following code runs as expected: > >> > > >> > set.seed(1) > >> > > >> > df1 <- data.frame(id1 = sample(1:1e2, 5e2, TRUE), > >> > id2 = sample(1:3, 5e2, TRUE), > >> > id3 = sample(1:5, 5e2, TRUE), > >> > val = sample(1:300, 5e2, TRUE)) > >> > > >> > df1$diff <- ave(df1$val, > >> > df1$id1, > >> > df1$id2, > >> > df1$id3, > >> > FUN = function(i) c(diff(i), 0)) > >> > > >> > head(df1[order(df1$id1, > >> > df1$id2, > >> > df1$id3), ]) > >> > > >> > But when expanding the data.frame (* 1e4), ave fails (Error: cannot > allocate vector of size 1110.0 Gb): > >> > > >> > df2 <- data.frame(id1 = sample(1:(1e2 * 1e4), 5e2 * 1e4, TRUE), > >> > id2 = sample(1:3, 5e2 * 1e4, TRUE), > >> > id3 = sample(1:(5 * 1e4), 5e2 * 1e4, TRUE), > >> > val = sample(1:300, 5e2 * 1e4, TRUE)) > >> > > >> > df2$diff <- ave(df2$val, > >> > df2$id1, > >> > df2$id2, > >> > df2$id3, > >> > FUN = function(i) c(diff(i), 0)) > >> > > >> > This use case does not seem extreme to me (e.g. aggregate et al work > perfectly on this data.frame). > >> > So my question is: Is this expected/intended/reasonable? i.e. Does > ave need to be optimized? > >> > > >> > > >> > > >> > 2) Gabor Grothendieck pointed out in 2011 that drop = TRUE is needed > to avoid warnings in case of unused levels ( > https://urldefense.com/v3/__https://stat.ethz.ch/pipermail/r-devel/2011-February/059947.html__;!!JQ5agg!J2AUFbQr31F2c6LUpTnyc5TX2Kh1bJ-VqhMND1c0N5axWO_tQl0pCJhtucPfjU7NXrBO$ > ). > >> > Is it relevant/possible to expose the drop argument explicitly? > >> > > >> > > >> > > >> > Thanks, > >> > > >> > Thomas > >> > ______________________________________________ > >> > R-devel@r-project.org mailing list > >> > > https://urldefense.com/v3/__https://stat.ethz.ch/mailman/listinfo/r-devel__;!!JQ5agg!J2AUFbQr31F2c6LUpTnyc5TX2Kh1bJ-VqhMND1c0N5axWO_tQl0pCJhtucPfjUzdLFM1$ > >> > >> ______________________________________________ > >> R-devel@r-project.org mailing list > >> https://stat.ethz.ch/mailman/listinfo/r-devel > [[alternative HTML version deleted]] ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel