[Rcpp-devel] Segfault error during simulation in Rcpp

[Ivan Popivanov]

How is this code supposed to work? If n=1e6, then the matrix has 1e12
elements, right? That's in the terabyte range - the memory manager is going
to blow up or overflow and the results would be unpredictable. Or am I
missing something?

Regards,
Ivan


On Thu, May 16, 2013 at 7:14 PM, Jonathan Olmsted <jpolmsted at gmail.com>wrote:

> Matteo,
>
>
>
>> The other obvious of course is that you are not forced to control a loop
>> over
>> 10^6 elements from R either:  pass N=10^6 down to C++ code, and run your N
>> loops there.  You will also get a considerable speed boost.
>>
>>
> ^ I could have been more explicit. This is what I meant. You might may or
> may not be able to do this in the sourceCpp() framework, though. How you do
> this is much more obvious if you go the route of making an Rcpp package.
> For as much as the convenience functions are a blessing, I've always found
> it hard to think about how I'd do more complex things with them. It could
> be possible, I just don't see it. I find the package approach to be a nice
> balance between abstracting away from some details but keeping some in the
> forefront of your mind. If you email me off the list and I can send you a
> very small package that using Rcpp. Multiple C++ functions are created,
> only some are exposed to R.
>
> It seems like you'd probably do something similar.
>
> -Jonathan
>
>
>
>
>
>>  | On Thu, May 16, 2013 at 8:11 PM, Dirk Eddelbuettel <edd at debian.org>
>> wrote:
>> |
>> |
>> |     On 16 May 2013 at 14:49, Jonathan Olmsted wrote:
>> |     | Several things.
>> |     |
>> |     | Xiao, Dirk's code gives me a segfault immediately and reliably.
>> |     |
>> |     | All, when I do this whole song and dance using the "old"
>> Rcpp/inline/
>> |     | cxxfunction approach, I don't have any issues. One obvious
>> difference you
>> |     can
>> |     | see (like was mentioned) in the generated code (visibile using
>> verbose=
>> |     TRUE) is
>> |     | the declaration of an RNGScope object.
>> |     |
>> |     | But, if the memory issue crops up when you call a C++
>> function (syncing
>> |     with
>> |     | R's RNG state) 1e6 times AND you are already writing C++ maybe
>> this is
>> |     an
>> |     | opportunity to just put one more layer of the code into C++ and
>> create
>> |     only one
>> |     | such RNGScope object?
>> |
>> |     Beautiful. So we get to blame R Core after all?  ;-)
>> |
>> |     Dirk
>> |
>> |     --
>> |     Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com
>> |     _______________________________________________
>> |     Rcpp-devel mailing list
>> |     Rcpp-devel at lists.r-forge.r-project.org
>> |
>> https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/rcpp-devel
>> |
>> |
>>
>> --
>> Dirk Eddelbuettel | edd at debian.org | http://dirk.eddelbuettel.com
>>
>
>
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