gc {base}R Documentation

Garbage Collection

Description

A call of gc causes a garbage collection to take place. gcinfo sets a flag so that automatic collection is either silent (verbose=FALSE) or prints memory usage statistics (verbose=TRUE).

Usage

gc(verbose = getOption("verbose"), reset=FALSE)
gcinfo(verbose)

Arguments

verbose logical; if TRUE, the garbage collection prints statistics about cons cells and the vector heap.
reset logical; if TRUE the values for maximum space used are reset to the current values

Details

A call of gc causes a garbage collection to take place. This takes place automatically without user intervention, and the primary purpose of calling gc is for the report on memory usage.

However, it can be useful to call gc after a large object has been removed, as this may prompt R to return memory to the operating system.

Value

gc returns a matrix with rows "Ncells" (cons cells), usually 28 bytes each on 32-bit systems and 56 bytes on 64-bit systems, and "Vcells" (vector cells, 8 bytes each), and columns "used" and "gc trigger", each also interpreted in megabytes (rounded up to the next 0.1Mb).
If maxima have been set for either "Ncells" or "Vcells", a fifth column is printed giving the current limits in Mb (with NA denoting no limit).
The final two columns show the maximum space used since the last call to gc(reset=TRUE) (or since R started).
gcinfo returns the previous value of the flag.

See Also

Memory on R's memory management, and gctorture if you are an R hacker. reg.finalizer for actions to happen upon garbage collection.

Examples

gc() #- do it now
gcinfo(TRUE) #-- in the future, show when R does it
x <- integer(100000); for(i in 1:18) x <- c(x,i)
gcinfo(verbose = FALSE)#-- don't show it anymore

gc(TRUE)

gc(reset=TRUE)

[Package base version 2.1.0 Index]