R memory limit warning vs "unable to allocate..."

Question

Does a memory warning affect my R analysis?

When running a large data analysis script in R I get a warning something like:

In '... ' reached total allocation of ___Mb: see help...

But my script continues without error, just the warning. With other data sets I get an error something like:

Error: cannot allocate vector of size ___Mb:

I know the error breaks my data analysis, but is there anything wrong with just getting the warning? I have not noticed anything missing in my data set but it is very large and I have no good means to check everything. I am at 18000Mb allocated to memory and cannot reasonably allocate more.

Answer 1

Way back in the R 2.5.1 news I found this reference to memory allocation warnings:

malloc.c has been updated to version 2.8.3. This version has a slightly different allocation strategy, and is likely to work a little better close to address space limits but may give more warnings about reaching the total allocation before successfully allocating.

Based on this note, I hypothesize (without any advanced knowledge of the inner implementation) that the warning is given when the memory allocation call in R (malloc.c) failed an attempt to allocate memory. Multiple attempts are made to allocate memory, possibly using different methods, and possibly with calls to the garbage collector. Only when malloc is fairly certain that the allocation cannot be made will it return an error.

Warnings do not compromise existing R objects. They just inform the user that R is nearing the limits of computer memory.

(I hope a more knowledgeable user can confirm this...)