<div dir="ltr"><br><br><div class="gmail_quote"><div dir="ltr"><div><div><div><div>update: came across Simon's <a href="http://lists.r-forge.r-project.org/pipermail/rcpp-devel/2013-June/006080.html" target="_blank">http://lists.r-forge.r-project.org/pipermail/rcpp-devel/2013-June/006080.html</a> post, where Romain suggested c++11 move constructor; which is supported in the latest Armadillo release; <br>
<br></div>for the record here are the tested working solutions, if found to be useful for others and there is a way to add these to RcppArmadillo examples, I can send the code in required format. <br><br></div><div>thanks again for everyone's contribution,<br>
</div><div>steve<br></div><div>/*<br></div><div>---------------------------------------------------------- code c++11 -------------------------------------------------------------------------<br></div><div><div class="im">
*/<br><br>#include <R.h><br>
#include <stdlib.h><br>#include <RcppArmadillo.h><br></div>#include <utility><div class="im"><br><br>using namespace std;<br><br>// [[Rcpp::depends(RcppArmadillo)]] <br><br><br></div></div>// suggested by Simon, pointer solution, this has a disadvantage of extra de referencing<br>
</div>// which is ok inside class methods, but somewhat awkward when matrix is public <br></div>// has the advantage that doesn't need c++11 and latest Armadillo<br><div><div><div><div>struct Example {<br><br> Example(double *ptr) {<br>
<br> A= new arma::mat(ptr, 3,2, false, true ); // same area as original B<br> arma::mat &a = *A; // dereference B<div class="im"><br> a(1,1) = 1; // convenient matlab like syntax<br>
} <br>
<br> ~Example(){ delete A; }<br></div> arma::mat *A;<br>};<br><br></div><div>// this is moving constructor works only with c++11 and latest Armadillo<br></div><div>// much nicer syntax; the 'view' is encapsulated, and invisible; <br>
</div><div>struct Example1 {<br><br> Example1(double *ptr ) : A(arma::mat(ptr, 3,2, false, true ) ){<br> A(1,1) = 3;<br> } <br> <br> arma::mat A;<br>};<br><br><div>// this is moving constructor works only with c++11 and latest Armadillo<br>
</div>// much nicer syntax, referenced matrix constructed with move contructor<br>struct Example2 {<br><br> Example2(arma::mat m ) : A(m){ // 'view' is not visible from the inside<br> A(2,1) = 4;<br>
} <br> <br> arma::mat &A;<div class="im"><br>};<br>// [[Rcpp::depends(RcppArmadillo)]] <br>// [[Rcpp::export]] <br>void arma_example() {<br><br></div> arma::mat M(3,10); // implicit memory allocation; of course this can be done many other ways<br>
</div><div> // Dirk suggestions using bigmemory and or R matrix passed with Rcpp proxy<br></div><div> // depending on needs<br></div><div class="im"><div> <br>
M.zeros(); // paint with zeros<br>
M.print(); cout<<endl<<endl;<br><br></div></div><div>// this is the main part: arma::mat submatrix has read write access to M without copy!;<br></div><div>// inside of Example? classes one can operate on some part of M <br>
</div><div> Example E(M.memptr());<br> M.print();cout<<"-------------"<<endl;<br> <br> Example1 E1( M.memptr() ); <br> M.print(); cout<<"-------------"<<endl;<br>
<br> Example2 E2( arma::mat( M.memptr(), 3,2, false, true ) ); <br> M.print();cout<<"-------------"<<endl;<br>}<br>// EOF<br><br><br><div><div><div><br><br><br></div></div></div></div>
</div></div></div></div><div class="HOEnZb"><div class="h5"><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Nov 26, 2013 at 7:38 PM, Steven Varga <span dir="ltr"><<a href="mailto:steven.varga@gmail.com" target="_blank">steven.varga@gmail.com</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex"><div dir="ltr"><div><div><div><div>Hello Simon,<br><br></div>my apologies contacting you off the list; I try to avoid confusion.<br>
<br></div>I came across your previous post: <a href="http://lists.r-forge.r-project.org/pipermail/rcpp-devel/2013-June/006080.html" target="_blank">http://lists.r-forge.r-project.org/pipermail/rcpp-devel/2013-June/006080.html</a> where you seemed to have similar issues to mine: creating an arma::mat with external storage, then bumping into '=' operator which does deep copy;<br>
<br></div>I just noticed that the newest version of Armadillo supports c++11 move constructor; did you have a chance to try it?<br><br></div>Steve<br></div><div><div><div class="gmail_extra"><br>
<br><div class="gmail_quote">On Tue, Nov 26, 2013 at 6:19 AM, <span dir="ltr"><<a href="mailto:szehnder@uni-bonn.de" target="_blank">szehnder@uni-bonn.de</a>></span> wrote:<br>
<blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">Steve,<br>
<br>
If you want to use a variable being an arma::mat obejct with varying memory, you could use an arma::mat pointer. Otherwise if memory stays the same but should be reusable in R, Dirk's suggestion initialising memory in R and passing it to C++ is the most practicable way and very fast.<br>
<br>
Best<br>
Simon<br>
Gesendet über den BlackBerry® Service von E-Plus.<br>
<br>
-----Original Message-----<br>
From: Steven Varga <<a href="mailto:steven.varga@gmail.com" target="_blank">steven.varga@gmail.com</a>><br>
Sender: rcpp-devel-bounces@lists.r-forge.r-project.orgDate: Mon, 25 Nov 2013 23:23:24<br>
To: <<a href="mailto:rcpp-devel@lists.r-forge.r-project.org" target="_blank">rcpp-devel@lists.r-forge.r-project.org</a>><br>
Reply-To: <a href="mailto:steven.varga@gmail.com" target="_blank">steven.varga@gmail.com</a><br>
Subject: Re: [Rcpp-devel] RcppArmadillo matrix with writeable auxiliary<br>
memory<br>
<br>
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