On Thu, Apr 1, 2010 at 8:57 AM, Dirk Eddelbuettel <[email protected]> wrote: > > On 30 March 2010 at 16:12, Romain Francois wrote: > | > It is not certain that those will be the same as the libraries used by > | > Armadillo. If they are not shared objects you run the risk of getting > | > two copies of Lapack, etc. and possibly different BLAS, leading to > | > different performance characteristics and perhaps different results. > | > | Hmmm. Interesting. I did not think of that problem. > | > | On my machine, I have : > | > | Rscript -e "RcppArmadillo:::LdFlags()" > | /Library/Frameworks/R.framework/Resources/library/Rcpp/lib/x86_64/libRcpp.a > | -L/usr/lib -larmadillo > | > | so linking against Rcpp "user" library and armadillo... but when I > | manually set PKG_LIBS to just Rcpp user library, it still works, so we > | actually do not need to link against armadillo library. armadillo itself > | does not __need__ to get compiled into a library because it is all > | templates. > > But "it still works" is no proof. We had talked about this once before (I > think) and I pointed you to the Armadillo FAQ which states that it _can_ be > used without LAPACK but _should_ be used with LAPACK (for performance). > > When you drop -llapack from the link line, the linker "simply" finds it via > R's library dependencies. So when Armadillo needs to find a Lapack routine > for inversion, it finds the one R uses. > > But I do not think we can turn that upside down and not link Arma with lapack > as R can be build in several configurations so I fear we'd end with some that > are suitable for Arma and some that may not be. > > So Doug's warning is a good one. > > OTOH this was meant to be a simple demo package and I simply do not want to > spend a day or so on configure et al to make it more complicated than it > already is.
Thanks for the clarification, Dirk. I had sort-of reached the same conclusion myself but not as well thought-out as yours. _______________________________________________ Rcpp-devel mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
