Re: [Rd] [R] R garbage collection

From: Luke Tierney <luke_at_stat.uiowa.edu>
Date: Fri 31 Mar 2006 - 15:29:24 GMT

The allocations described as User-Controlled are not part of the GC-managed heap. The ones described as Transient happen to be but that is not user visible; alternate implementations might insure that they are freed as soon as the appropriate context is left.

If you are interested in managing the lifetime of heap-allocated objects then you register roots for the GC with R_PreserveObject.

luke

On Fri, 31 Mar 2006, Prof Brian Ripley wrote:

> On Thu, 30 Mar 2006, Jeff Henrikson wrote:
>
>> r-help,
>
> [Moved to R-devel.]
>
>> The R manual lists two types of memory: transient and user-controlled.
>> If I have transient blocks reachable from the globals only by traversal
>> through user-controlled blocks, will they be correctly preserved?
>
> I don't understand your terminology, especially 'traversal'. It is not
> normal to have either type of block reachable through R objects, and if
> you are using something like external pointers, the answer would be no.
>
>> Secondly, what are the ways to mark user controlled blocks as "roots"
>> for the garbage collector, so that transient blocks they reference stay
>> uncollected? So far I can only deduce that as long as the answer to my
>> first question is yes, I can bind an arbitrary symbol to them in the
>> global environment. Is this the best way?
>
> I think you are referring to blocks allocated by R_alloc. The manual says
>
> This memory is taken from the heap, and released at the end of the .C,
> .Call or .External call. Users can also manage it, by noting the current
> position with a call to vmaxget and clearing memory allocated
> subsequently by a call to vmaxset. This is only recommended for experts.
>
> If you want to allocate storage as part of an R object, this is not the
> best way to do it (allocVector etc are). It is a side-effect of the
> current implementation that memory allocated by R_alloc which is made part
> of an object will be protected for the lifetime of that object, but this
> is not documented and should not be relied on. (I am thinking if for
> example a block is made into a CHARSXP 'by hand', but the documented route
> is mkChar which makes a copy.)
>
>> Jeff Henrikson
>>
>> PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html
>
> Please do, including the question `which list': this clearly belongs on
> R-devel.
>
>

-- 
Luke Tierney
Chair, Statistics and Actuarial Science
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
241 Schaeffer Hall                  email:      luke@stat.uiowa.edu
Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu

______________________________________________
R-devel@r-project.org mailing list
https://stat.ethz.ch/mailman/listinfo/r-devel
Received on Sat Apr 01 01:52:48 2006

This archive was generated by hypermail 2.1.8 : Fri 31 Mar 2006 - 18:16:42 GMT