On 24 June 2015 at 08:22, Charles Determan wrote:
| Thank you John,
|
| I am familiar with bigmemory (I am one of the current developers actually).
| The project I am working on doesn't need the shared memory aspect so was
| intending to avoid the dependency and just leverage the more familiar and
| developed Armadillo library. However your response informs me that I did not
| fully understand how armadillo objects are handled. I have some other ideas
| with how I can address my problem but this was something I was hoping to apply
| both for this project and for the sake of learning.
Look at more current RcppArmadillo examples, and in particular _all_ the
variants of the fastLm benchmark in examples. By doing the explicit cast,
you _forced_ a copy which may then have destroyed the Xptr link. I *think*
you could just do XPtr around arma::mat innards. I would actually be
interested in having something somewhere between bigmemory (where I was one
of the first external users) and what we have in RcppArmadillo.
Dirk, during a break of Rcpp class in Zuerich
| Regards,
| Charles
|
| On Tue, Jun 23, 2015 at 9:29 PM, John Buonagurio <jbuonagu...@exponent.com>
| wrote:
|
| Hi Charles,
|
| > SEXP testXptr(SEXP A)
| > {
| > arma::Mat<double> armaMat = Rcpp::as<arma::Mat<double> >(A);
| > Rcpp::XPtr<double> pMat(armaMat.memptr());
| > return(pMat);
| > }
|
| armaMat is on the stack, so the Armadillo memptr is no longer valid when
| you return from the testXptr function.
|
| One simple solution in your case would be to dynamically allocate with
| "new" [e.g. arma::mat *A = new arma::mat(...);], though I can't tell you
| off hand how object lifetime is managed with Armadillo objects.
|
| If you're trying to preserve a matrix across function calls in R, have you
| looked into bigmemory? http://gallery.rcpp.org/articles/
| using-bigmemory-with-rcpp/
|
| John
|
|
|
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--
http://dirk.eddelbuettel.com | @eddelbuettel | e...@debian.org
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