[R] [R-sig-hpc] recursion depth limitations

[Simon Urbanek]

On Dec 13, 2012, at 10:45 AM, Suzen, Mehmet wrote:

> Hello List,
> 
> I am aware that one can set with recursion depth 'options(expressions
> = #)', but it has 500K limit. Why do we have a 500K limit on this?

Because it's far beyond what you can handle without changing a lot of other things. 500k expressions will require at least about 320Mb of stack (!) in the eval() chain alone -- compare that to the 8Mb stack size which is default in most OSes, so you'll hit the wall way before that limit is reached.


> While some algorithms are only "solvable"  feasibility with recursion
> and 500K sounds not too much i.e. graph algorithms
> for example dependency trees with large nodes easily reach to that number.
> 

I don't see how "large nodes" have anything to do with this since we are talking about expression depth, not about sizes of any kind. Again, in any realistic example you'll hit other limits first anyway.

Cheers,
Simon