[R] Problem with mclapply -- losing output/data

[Janet Young]

Hi Elizabeth,

I just found your thread after experiencing a similar problem (I was also 
using some IRanges/GenomicRanges functions).  You've probably figured it 
out by this time - I'm actually curious to know what you found?

I think I've tracked it down in my case, where a small minority of the 
elements I was trying to lapply/mclapply over caused a genuine error 
(perhaps in your case a genuine NULL answer - is that possible?).  When 
I used lapply that error was very obvious - it came up on the screen.  
But when I used mclapply it looked like the function completed fine - 
it wasn't until later that I saw the error was captured as a string 
object in the relevant slot of  the list object returned by mclapply.  
I should build in some checking if I want to persist with using 
mclapply.

I wonder if something similar is going on in your case? 

Janet