A new package of ours, RcppNLoptExample, arrived on CRAN yesterday after a somewhat longer-than-usual wait for new packages as CRAN seems really busy these days. As always, a big and very grateful Thank You! for all they do to keep this community humming.
So what does it do ?
Starting with its 1.2.0 release, the nloptr package now exports several C symbols in a way that makes it accessible to other R packages without linking easing the installation on all operating systems.
How / Why ?
R uses C interfaces. These C interfaces can be exported between packages. So when the usual
library(nloptr) (or an import via
NAMESPACE) happens, we now also get a number of C functions registered.
And those are enough to run optimization from C++ as we simply rely on the C interface provided. Look careful at the example code: the objective function and the constraint functions are C functions, and the body of our example invokes C functions from NLopt. This just works. For either C code, or C++ (where we rely on Rcpp to marshal data back and forth with ease).
On the other hand, if we tried to use the NLopt C++ interface which brings with it someinterface code we would require linking to that code (which R cannot easily export across packages using its C interface). So C it is.
The package is pretty basic but fully workable. Some more examples should get added, and a helper class or two for state would be nice. The (very short) NEWS entry follows:
Changes in version 0.0.1 (2018-10-01)
- Initial basic package version with one example from NLopt tutorial
Code, issue tickets etc are at the GitHub repository.