[Rd] strange increase in the reference number

brodie gaslam brod|e@g@@|@m @end|ng |rom y@hoo@com
Sat Jul 13 20:19:30 CEST 2019

Re ENSURE_NAMEDMAX, I am unsure but think this happens in (src/eval.c using 492):
 static SEXP forcePromise(SEXP e)
    if (PRVALUE(e) == R_UnboundValue) {
    /* ... SNIP ...*/
    val = eval(PRCODE(e), PRENV(e));
    /* ... SNIP ...*/
    SET_PRSEEN(e, 0);
    SET_PRVALUE(e, val);
    ENSURE_NAMEDMAX(val);                 <<<<<<< HERE
    SET_PRENV(e, R_NilValue);
    return PRVALUE(e);

as part of the evaluations of the closure.  `forcePromise` is called ineval (src/eval.c using 656).  It's been a while since I've looked at the mechanicsof how the native version of `eval` works so I could be completely wrong.


PS: line references are in r-devel using 76287.

On Friday, July 12, 2019, 4:38:06 PM EDT, Gabriel Becker <gabembecker using gmail.com> wrote: 

Hi Jiefei and Duncan,

I suspect what is likely happening is that one of  ENSURE_NAMEDMAX or
MARK_NOT_MUTABLE are being hit for x. These used to set named to 3, but now
set it to 7 (ie the previous and current NAMEDMAX  value, respectively).

Because these are macros rather than C functions, its not easy to figure
out why one of them is being invoked from do_isvector  (a cursory
exploration didn't reveal what was going on, at least to me) and I don't
have the time to dig super deeply into this right now,  but perhaps Luke or
Tomas know why this is happening of the top of their head.

Sorry I can't be of more help.


On Fri, Jul 12, 2019 at 11:47 AM Duncan Murdoch <murdoch.duncan using gmail.com>

> On 12/07/2019 1:22 p.m., King Jiefei wrote:
> > Hi,
> >
> > I just found a strange increase in the reference number and I'm wondering
> > if there is any reason for it, here is the code.
> >
> >> a=c(1,2,3)
> >> .Internal(inspect(a))
> > @0x000000001bf0b9b0 14 REALSXP g0c3 [NAM(1)] (len=3, tl=0) 1,2,3
> >> is.vector(a)
> > [1] TRUE
> >> .Internal(inspect(a))
> > @0x000000001bf0b9b0 14 REALSXP g0c3 [NAM(7)] (len=3, tl=0) 1,2,3
> >
> > The variable *a* initially has one reference number, after calling
> > *is.vector* function, the reference number goes to 7, which I believe is
> > the highest number that is allowed in R.  I also tried the other R
> > functions, *is.atomic, is.integer* and *is.numeric* do not increase the
> > reference number, but *typeof *will do. Is it intentional?
> is.vector() is a closure that calls .Internal.  is.atomic(),
> is.integer() and is.numeric() are all primitives.
> Generally speaking closures that call .Internal are easier to implement
> (e.g. is.vector can use the regular mechanism to set a default for its
> second argument), but less efficient in CPU time.  From it's help page,
> it appears that the logic for is.vector() is a lot more complex than for
> the others, so that implementation does make sense.
> So why does NAMED go to 7?  Initially, the vector is bound to a.  Within
> is.vector, it is bound to the local variable x.  At this point there are
> two names bound to the same object, so it has to be considered
> immutable.  There's really no difference between any of the values of 2
> or more in the memory manager.  (But see
> http://developer.r-project.org/Refcnt.html for some plans.  That
> document is from about 5 years ago; I don't know the current state.)
> Duncan Murdoch
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> R-devel using r-project.org mailing list
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