On Jul 5, 2009, at 10:54 AM, Yuri D'Elia wrote:
Hi everybody,
I have been interfacing some C++ library code into an R package but
ran into optimization issues specific to memory management that
require
some insight into the GC.
One of the C++ libraries returns simple vectors of integers, doubles
and
complex which are allocated and managed from the library itself. I
cannot know the length of the array beforehand, so I cannot
pre-allocate that memory through the GC.
Right now I'm allocating via allocVector and copying all the data in
it.
However, this requires twice the amount of space (and time), and we're
running out of memory when doing concurrent analysis.
What I'd would like to do is:
- "patch" the SEXP returned to R so that DATAPTR() points directly to
the required address.
Why don't you just "patch" the library to use allocVector? That's most
reliable and trivial to do. Messing around with internal SEXP
representation is asking for trouble as that may change at any point
without notice (note that all access is through functions to avoid
that).
Cheers,
Simon
- create a normal LISTSXP in the package, which holds a reference
to all these objects, so that GC never takes place.
- turn these objects read-only, or, at least, ensure that they are
never free()d or remalloc()ed. overwriting the contents is not a
critical issue.
Would that approach work?
Are there any alternative approaches?
Any specific advice about turning these objects read-only?
Thanks in advance.
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