Hi Dirk,
I take your point. Given that the conversion is essentially free, temporary
conversion makes the most sense.
Thank you again!
Jon
On Wed, Oct 12, 2016 at 2:36 PM, Dirk Eddelbuettel <e...@debian.org> wrote:
>
> Hi Jon,
>
> On 12 October 2016 at 14:20, Jonathan Fintzi wrote:
> | Thanks for the quick response. In the broader project, the vector being
> copied
> | from is an Rcpp::NumericVector that contatenates vectorized versions of a
> | number of other objects that are integrated numerically using the boost
> odeint
> | solvers. I couldn't quite get the numerical integrators to play nice with
> | Armadillo objects, and in using std::copy I was trying to avoid
> converting the
> | vector 'v' to an arma::vec since I would have to convert it back for
> further
> | integration. Perhaps this was a mistake?
>
> Yes -- the transformation in as essentially costless. We have some
> benchmarking that show that.
>
> | Still, I don't quite understand why armadillo row pointers don't work
> which
> | armadillo column pointers are fine.
>
> Now you phrase your question as "arma-only" (which makes sense) but that
> is not what your code does, is it?
>
> I see that you are having an issue mixing things. So I suggest an easy
> simplification. You are of course free to ignore that -- but you may then
> have to provide another layer as the compiler so far appears to be unhappy.
>
> Dirk
>
> | Thanks,
> | Jon
> |
> | On Wed, Oct 12, 2016 at 2:10 PM, Dirk Eddelbuettel <e...@debian.org>
> wrote:
> |
> |
> | On 12 October 2016 at 13:43, Jonathan Fintzi wrote:
> | | Hello,
> | |
> | | I am trying to use the std::copy() function to copy elements from
> an
> | | Rcpp::NumericVector into rows of armadillo matrices. A simplified
> version
> | of my
> | | code is as follows:
> | |
> | | cppFunction('void copyinto(Rcpp::NumericVector& v, arma::mat& d1,
> | arma::mat&
> | | d2) {
> | | std::copy(v.begin(), v.begin() + 3, d1.begin_row(0));
> | | std::copy(v.begin() + 3, v.end(), d2.begin_row(0));
> | | }', depends = "RcppArmadillo")
> |
> | You should not need to mix an _Rcpp_ vector with an _Armadillo_
> matrix
> | using
> | std::copy. Check the decent Armadillo docs -- all the subsetting and
> | slicing
> | can be done with Armadillo. And that is what I would do.
> |
> | But maybe I didn't quite understand what you are really after.
> |
> | Dirk
> |
> | | v <- runif(6)
> | | d1 <- matrix(0.0, 3,3)
> | | d2 <- matrix(0.0, 3,3)
> | |
> | | copyinto(v, d1, d2)
> | |
> | | However, when I attempt to compile the code, I receive a list of
> | compilation
> | | errors including "no type named 'XXXXXX' in 'class
> arma::Mat<double>
> | | row_iterator", where XXXXXX is iterator_category, value_type,
> | difference_type,
> | | pointer, and reference.
> | |
> | | If I change the iterators to column iterators (e.g.
> d1.begin_col(0))
> | everything
> | | compiles and works just fine. I feel that I must be missing
> something
> | quite
> | | basic here, but in searching around I haven't been able to
> identify my
> | mistake.
> | |
> | | Thank you for your help!
> | | Jon
> | | _______________________________________________
> | | 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
> |
> | --
> | http://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org
> |
> |
>
> --
> http://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org
>
_______________________________________________
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
