Hi Simon,
On 26 Feb 2007, at 16:58, Simon Urbanek wrote:
> Ernest,
>
> On Feb 25, 2007, at 12:37 PM, Ernest Turro wrote:
>
>> I have wrapped a C++ function in an R package. I allocate/
>> deallocate memory using C++ 'new' and 'delete'. In order to allow
>> user interrupts without memory leaks
>
> How do you allow for user interrupts? R doesn't allow interrupts
> while in .C/.Call on purpose,
void R_CheckUserInterrupt(void)
> so it's up to your code to handle interrupts properly. This also
> implies that you can use the regular methods for error recovery
> available in your language and handle the interrupt yourself by
> freeing the memory as needed, your code shouldn't return to R until
> it has cleaned everything up ...
How can I detect an interrupt from R inside the C/C++ code without
using the R API? SIGINTs don't get passed on if they come from within
R...
>
>
>> I've moved all the delete statements required after an interrupt
>> to a separate C++ function freeMemory(), which is called using
>> on.exit() just before the .C() call.
>>
>
> This sounds a bit dangerous - how can the separate function know
> about the previous call and the state it was in before the
> interrupt (save for hard-wiring everything into one instance)?
> Again, the crucial part is the interrupt handling in your code - it
> may fail to release some objects...
>
I have to declare variables for any allocated memory globally:
static int foo*;
extern "C"
void func(...) {
foo = new int[1024];
// heavy computation
// inside loop:
R_CheckUserInterrupt()
//end heavy computation
}
extern "C"
void freemem(...) {
delete [] foo;
}
in R:
func <- function() {
on.exit(.C("freemem"))
.C("func")
}
Cheers,
Ernest
> @Ross [see follow-up]: R_RegisterCFinalizerEx is called on R exit
> if desired (see arguments). However, I don't think this is relevant
> to the discussed issue as a process termination frees all its
> memory. Moreover I don't think Ernest wants to wrap all his classes
> to R objects - we're not talking about the GC here, it is supposed
> to be C++ internal issue.
>
> Cheers,
> Simon
>
>
>> I am concerned about the following. In square brackets you see R's
>> total virtual memory use (VIRT in `top`):
>>
>> 1) Load library and data [178MB] (if I run gc(), then [122MB])
>> 2) Just before .C [223MB]
>> 3) Just before freeing memory [325MB]
>> 4) Just after freeing memory [288MB]
>> 5) After running gc() [230MB]
>>
>> So although the freeMemory function works (frees 37MB), R ends up
>> using 100MB more after the function call than before it. ls() only
>> returns the data object so no new objects have been added to the
>> workspace.
>>
>> Do any of you have any idea what could be eating this memory?
>>
>> Many thanks,
>>
>> Ernest
>>
>> PS: it is not practical to use R_alloc et al because C++ allocation/
>> deallocation involves constructors/destructors and because the C++
>> code is also compiled into a standalone binary (I would rather avoid
>> maintaining two separate versions).
>>
>> ______________________________________________
>> R-devel@r-project.org mailing list
>> https://stat.ethz.ch/mailman/listinfo/r-devel
>>
>>
>
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