[Rd] segfault when trying to allocate a large vector

[Pierrick Bruneau]

Hi Karl,

I thought I had also tried to allocate on the heap - just tried again,
and everything went fine (even up to 10^9 cells). I guess everything's
OK then ^^
Thanks for your help!

Pierrick

On Thu, Dec 18, 2014 at 9:44 AM, Karl Millar <kmillar at google.com> wrote:
> Hi Pierrick,
>
> You're storing largevec on the stack, which is probably causing a stack
> overflow.  Allocate largvec on the heap with malloc or one of the R memory
> allocation routines instead and it should work fine.
>
> Karl
>
> On Thu, Dec 18, 2014 at 12:00 AM, Pierrick Bruneau <pbruneau at gmail.com>
> wrote:
>>
>> Dear R contributors,
>>
>> I'm running into trouble when trying to allocate some large (but in
>> theory viable) vector in the context of C code bound to R through
>> .Call(). Here is some sample code summarizing the problem:
>>
>> SEXP test() {
>>
>> int size = 10000000;
>> double largevec[size];
>> memset(largevec, 0, size*sizeof(double));
>> return(R_NilValue);
>>
>> }
>>
>> If size if small enough (up to 10^6), everything is fine. When it
>> reaches 10^7 as above, I get a segfault. As far as I know, a double
>> value is represented with 8 bytes, which would make largevec above
>> approx. 80Mo -> this is certainly large for a single variable, but
>> should remain well below the limits of my machine... Also, doing a
>> calloc for the same vector size leads to the same outcome.
>>
>> In my package, I would use large vectors that cannot be assumed to be
>> sparse - so utilities for sparse matrices may not be considered.
>>
>> I run R on ubuntu 64-bit, with 8G RAM, and a 64-bit R build (3.1.2).
>> As my problem looks close to that seen in
>> http://r.789695.n4.nabble.com/allocMatrix-limits-td864864.html,
>> following what I have seen in ?"Memory-limits" I checked that ulimit
>> -v returns "unlimited".
>>
>> I guess I must miss something, like contiguity issues, or other. Does
>> anyone have a clue for me?
>>
>> Thanks by advance,
>> Pierrick
>>
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