Jens, On Mar 3, 2014, at 3:35 PM, Jens Oehlschlägel <jens.oehlschlae...@truecluster.com> wrote:
> Thanks for answering Simon, > > > None, there is no concept of "shared" memory at R level. You seem to be > > mixing C level API specifics and the R language. In the former duplicate() > > creates a new copy. > > I take this as evidence that calling duplicate() is the only way to make sure > I have a non-shared object. > If NAMED > 0 then calling duplicate() is necessary to make sure you have a non-shared copy. > > Assuming that you are talking about the C API, please consider reading > > about the concepts involved. .Call() doesn't set named to 2 at all - it > > passes whatever object is passed so it is the C code's responsibility to > > handle incoming objects according to the desired semantics (see the > > previous post here). > > Well, I did read, for example "Writing R Extensions" (Version 3.1.0 Under > development (2014-02-28)) chapter "5.9.10 Named objects and copying" which > says "Currently all arguments to a .Call call will have NAMED set to 2, and > so users must assume that they need to be duplicated before alteration." Matthew pointed out that line and I cannot shed more light on it, since it's not true - at least not currently. > This is consistent with the observation of my test code: that NAMED() in > .Call always returns 2. It is not - you're not testing .Call() - your'e testing the assignments in frames which cause additional bumps of NAMED. If you actually test .Call() you'll see what I have reported - .Call() itself does NOT affect NAMED. > And that a .Call doing pure read access will trigger some delay most likely > due to a full vector copy is a sign of .Call not only setting NAMED to 2 but > also not resetting it once .Call terminates. > Again, as I said earlier, you're on the wrong track here - .Call() doesn't touch it - it is left to the C code. Note that NAMED cannot be decremented (unless you use a ref counting version of R) once it reaches 2 since that means "two or more" so. The only time where you can decrement it is if you are the owner that set it from 0 to 1. Cheers, Simon > So what is needed to find NAMED(SEXP argument) < 2 during .Call? > > Kind regards > > Jens > ______________________________________________ R-devel@r-project.org mailing list https://stat.ethz.ch/mailman/listinfo/r-devel
