Delete temporary environment variable and free memory in R

Question

I am working on a task in which a temporary hash table is reused through a loop. The Hash table is represented by the environment variable in R. The problem is that as the cycle continues, the cost of memory continues to rise no matter what method I used to delete the table (I tried rm() and gc() , however, none of them could free up memory.) As a result, I cannot execute an unusual long cycle, say, 10M cycles. This seems like a memory leak problem, but I cannot find a solution elsewhere. I would like to ask what is the right way to completely remove the environment variable and at the same time free up all the memory that it previously occupied. Thanks in advance for helping me verify the problem for me.

Here is a very simple example. I am using Windows 8 and R version 3.1.0.

 > fun = function(){ H = new.env() for(i in rnorm(100000)){ H[[as.character(i)]] = rnorm(100) } rm(list=names(H), envir=H, inherits=FALSE) rm(H) gc() } > > for(k in 1:5){ print(k) fun() gc() print(memory.size(F)) } [1] 1 [1] 40.43 [1] 2 [1] 65.34 [1] 3 [1] 82.56 [1] 4 [1] 100.22 [1] 5 [1] 120.36 

Answer 1

Environments in R are not a good choice for situations where keys can vary greatly in computing. The reason is that the environment requires the keys to be characters, and the characters not to be garbage collected. Thus, each run of your function adds to the internal character table. Arranging characters for garbage collection will be one option, although help will be needed, as many internal codes suggest that they are not. Another option is to create better hash table support so that environments do not try to use this purpose for which they were not originally designed.