I suspect that rbind is responsible. Use list and append instead of rbind. At the end, combine elements of list by do.call(“rbind”, list).
> On 17 Sep 2016, at 15:05, Philippe de Rochambeau <phi...@free.fr> wrote: > > Hello, > the following function, which stores numeric values extracted from a binary > file, into an R matrix, is very slow, especially when the said file is > several MB in size. > Should I rewrite the function in inline C or in C/C++ using Rcpp? If the > latter case is true, how do you « readBin » in Rcpp (I’m a total Rcpp > newbie)? > Many thanks. > Best regards, > phiroc > > > ------------- > > # inputPath is something like > http://myintranet/getData?pathToFile=/usr/lib/xxx/yyy/data.bin > <http://myintranet/getData?pathToFile=/usr/lib/xxx/yyy/data.bin> > > PLTreader <- function(inputPath){ > URL <- file(inputPath, "rb") > PLT <- matrix(nrow=0, ncol=6) > compteurDePrints = 0 > compteurDeLignes <- 0 > maxiPrints = 5 > displayData <- FALSE > while (TRUE) { > periodIndex <- readBin(URL, integer(), size=4, n=1, > endian="little") # int (4 bytes) > eventId <- readBin(URL, integer(), size=4, n=1, > endian="little") # int (4 bytes) > dword1 <- readBin(URL, integer(), size=4, signed=FALSE, n=1, > endian="little") # int > dword2 <- readBin(URL, integer(), size=4, signed=FALSE, n=1, > endian="little") # int > if (dword1 < 0) { > dword1 = dword1 + 2^32-1; > } > eventDate = (dword2*2^32 + dword1)/1000 > repNum <- readBin(URL, integer(), size=2, n=1, endian="little") > # short (2 bytes) > exp <- readBin(URL, numeric(), size=4, n=1, endian="little") # > float (4 bytes, strangely enough, would expect 8) > loss <- readBin(URL, numeric(), size=4, n=1, endian="little") # > float (4 bytes) > PLT <- rbind(PLT, c(periodIndex, eventId, eventDate, repNum, > exp, loss)) > } # end while > return(PLT) > close(URL) > } > > ---------------- > [[alternative HTML version deleted]] > > ______________________________________________ > R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see > https://stat.ethz.ch/mailman/listinfo/r-help > PLEASE do read the posting guide http://www.R-project.org/posting-guide.html > and provide commented, minimal, self-contained, reproducible code. ______________________________________________ R-help@r-project.org mailing list -- To UNSUBSCRIBE and more, see https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
