[R] Two Questions on R (call by reference and pre-compilation)

[Duncan Murdoch]

On 04/05/2010 5:05 PM, Ruihong Huang wrote:
> Hi All,
>
> I have two questions on R. Could you please explain them to me? Thank you!
>
> 1) When call a function, R typically copys the values to formal 
> arguments (call by value). This is very cost, if I would like to pass a 
> huge data set to a function. Is there any situations that R doesn't copy 
> the data, besides pass data in an environment object.
>   

R doesn't copy data unless it needs to, for example if your function 
modifies its copy.  So don't worry about the cost, there usually isn't 
much of one.
> 2) Does R pre-compile the object function to binary when running 
> "optim"? I experienced the R "optim" is much slower than the MATLAB 
> "fmincon" function. I don't know MATLAB has done any pre-compilation on 
> the script for object function or not. But perhaps, we can increase R 
> performance by some sort of pre-compilation during running time.
>   

There's an experimental compiler, but I don't know if there's a 
predicted release date for it.  R is not an easy language to compile.

Duncan Murdoch
>
> Thanks in advance.
>
>
> Best Regards,
> Ruihong
>   
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