Le 07/06/13 13:09, Simon Zehnder a écrit :
HI Dirk, hi Romain,
allright, this is now clear to me, if I want to reuse memory, the allocated
memory from R (so implicitly in C) must of course have the same type -
otherwise the memory has a different size.
so far, this is obvious.
On the other side I then assume, that the Rcpp:as<class M>() function makes a
cast and therefore creates a copy with new allocated memory of the type included in
M? Therefore a reuse of memory with this function is not possible.
Depends what is M, but most of the time yes, as<> copies data.
Best
Simon
On Jun 6, 2013, at 8:31 PM, Dirk Eddelbuettel <e...@debian.org> wrote:
On 6 June 2013 at 13:17, Dirk Eddelbuettel wrote:
|
| On 6 June 2013 at 19:05, Simon Zehnder wrote:
| | sorry I had overseen this message from you. Okay, so the explicit cast to
SEXP together with the assignment operator makes the deal. But it still
includes the reuse of memory right, i.e. the '=' does not call the copy
constructor?
|
| But how could an _unsigned int_ from Armadillo possibly have the same value
| as a _signed int_ in R?
|
| Either you are efficient (no copy), or you are correct (with a copy). I do
| not see how you could have both.
Sorry -- please ignore this message.
I had mistakenly assumed that you were still thinking about arma::umat to
integer. For direct int-to-int this is indeed efficient just like the
double-to-double is for arma::mat to NumericMatrix (and dito for vectors). I
though that was a given -- maybe need to make this (even) more explicit in
the documentation.
So in sum: you get correct and efficient behaviour if and only if you stick
with the types natively supported in Armadillo and R.
Dirk
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