Thanks Dirk! I worked a lot on it already yesterday.
Regarding OpenMP: I haven't yet found the underlying data structure for SEXPs but there should be something in the R Internals Guide. As the first-touch-principle has to be applied when the memory is allocated, I would rather copy the data from an SEXP to an arma::mat and run the '#pragma' over the arma::mat. So for allocating I have to pass an arma::mat an array, that is already allocated via first-touch. memptr() should do this work. I hope, though, that it does not copy the array :) Best Simon On Feb 2, 2013, at 4:17 PM, Dirk Eddelbuettel <e...@debian.org> wrote: > > Hi Simon, > > Welcome to the list. > > On 2 February 2013 at 14:47, Simon Zehnder wrote: > | Dear Rcpp-Devels, > | > | this list was suggested to me by Dirk Eddelbüttel in regard to a question > using C++ Extensions in relation with the Armadillo library. > | > | At first I have to make compliments to the developers of > Rcpp/RcppArmadillo. Dirk, Francois, this is a marvelous work! As someone > programming a lot in C++ and using R Extensions regularly, it is cleaning > away all this cumbersome programming dirt connected to SEXPs. > > Thanks. > > | There are still remaining questions for me, which can be surely answered by > the subscribers to this list: > | > | 1. I saw the Rcpp.package.skeleton function and I ask myself, if a similar > offer is made for RcppArmadillo for including automatically the Armadillo > library in a package? > > Sure -- there is RcppArmadillo.package.skeleton() in the RcppArmadillo > package. Dito for RcppGSL and RcppEigen. > > | 2. If I want to use Armadillo solely in the C++ files, not via inline > functions as shown in the RcppArmadillo paper, should I use solely the Rcpp > package? No, right? The RcppArmadillo package provides objects wrappers for > Armadillo objects to be passed to R? > > If you want just C++ from R, use Rcpp. > > If you want C++ and Armadillo from R, use RcppArmadillo. It depends on Rcpp > and brings it in. > > Etc pp for other libraries. Rcpp and RcppArmadillo should provide the > scaffolding to build upon. > > | 3. My package is based on S4 classes and I saw the S4 class wrapping in the > Rcpp package. I miss an example on this. Can you refer to any document or > website for this issue? > > Look at the Rcpp documentation, including the recently introduced Rcpp > Gallery at http://gallery.rcpp.org for some examples. I don't use S4 all > that much so I do not write many examples, but eg in RcppEigen context a few > more are found (as some of that work was motivated bty sparse matrices which > already have an S4 representation in R). > > | 4. Further: What is your experience regarding performance with S4 classes > and OOP in C++: Does it make a difference mapping the S4 class to a struct in > C++ or using directly the attributes of the S4 class (like vectors, etc.) as > Armadillo vectors etc. in C++? > | As I work a lot on the HPC in Aachen/Germany together with some of the > contributors to the OpenMP API, I am highly influenced by the parsimonious > approach, i.e. use only basic objects in C++ to get high performance > (although I know, that one of the main work now in the OpenMP API is the > extension to complex/user-defined objects inside the #pragmas). > > As I said, I do not use S4 all that much. But I am in favour of OOP :) > > | 5. Using OpenMP with RcppArmadillo: Up to now I used almost exclusively the > Scythe Statistical Library (http://scythe.wustl.edu), which is pretty fast. I > encountered lately problems with it, using parallel computing (OpenMP). Also > important in this regard is the possibility to apply a > 'first-touch-principle' where all my approaches failed in Scythe, due to the > object structure. > | Now, I would like to use RccpArmadillo with OpenMP and > | a) I want to get best performance: how would I proceed? > > Just do it. We have OpenMP examples in the Rcpp docs. Ensure you have locks > from R, do not call back, and it tends to just work to be "multithreaded in > chunks" at the C++ level.. > > Scythe was very important and a first C++ library for R when it came out. I > could imagine that Armadillo is faster, but I have not seen comparisons. > > | b) I want to apply the 'first-touch-principle': where do I > apply it? What is the internal data structure in Rcpp-/RcppArmadillo-Objects > that allocates the memory? > > It's whatever you would do with native R objects at the C level, only easier > :) > > | I am very excited now to start work with the Rcpp/RcppArmadillo package in > my own one, which is at least planned to be pushed to CRAN one day. > > We look forward to your contributions. These are open projects, so if you > can think of patches to code or documentation, please let us know. > > | I am looking forward to your answers > > Hope this helps. > > Dirk > > | > | Best > | > | Simon > | _______________________________________________ > | Rcpp-devel mailing list > | Rcpp-devel@lists.r-forge.r-project.org > | https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel > > -- > Dirk Eddelbuettel | e...@debian.org | http://dirk.eddelbuettel.com _______________________________________________ Rcpp-devel mailing list Rcpp-devel@lists.r-forge.r-project.org https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
