R: Memory Available for Data Storage

Memory {base} | R Documentation

## Memory Available for Data Storage

### Description

Use command line options to control the memory available for R.

### Usage

    R --min-vsize=vl --max-vsize=vu --min-nsize=nl --max-nsize=nu

    mem.limits(nsize = NA, vsize = NA)

### Arguments

`vl, vu, vsize` | Heap memory in bytes.
`nl, nu, nsize` | Number of cons cells.

### Details

R has a variable-sized workspace (from version 1.2.0). There is now much less need to set memory options than previously, and most users will never need to set these. They are provided both as a way to control the overall memory usage (which can also be done by operating-system facilities such as `limit` on Unix), and since setting larger values of the minima will make R slightly more efficient on large tasks.

To understand the options, one needs to know that R maintains separate areas for fixed and variable sized objects. The first of these is allocated as an array of ``cons cells'' (Lisp programmers will know what they are, others may think of them as the building blocks of the language itself, parse trees, etc.), and the second are thrown on a ``heap'' of ``Vcells'' of 8 bytes each. Effectively, the input `v` is rounded up to the nearest multiple of 8.

Each cons cell occupies 28 bytes on a 32-bit machine, (usually) 56 bytes on a 64-bit machine.

The `--*-nsize` options can be used to specify the number of cons cells and the `--*-vsize` options specify the size of the vector heap in bytes. Both options must be integers or integers followed by `M`, `K`, or `k` meaning Mega (2^{20} = 1048576), (computer) Kilo (2^{10} = 1024), or regular kilo (1000).

The `--min-*` options set the minimal sizes for the number of cons cells and for the vector heap. These values are also the initial values, but thereafter R will grow or shrink the areas depending on usage, but never exceeding the limits set by the `--max-*` options nor decreasing below the initial values.

The default values are currently minima of 350k cons cells, 6Mb of vector heap and no maxima (other than machine resources). The maxima can be changed during an R session by calling `mem.limits`. (If this is called with the default values, it reports the current settings.)

You can find out the current memory consumption (the heap and cons cells used as numbers and megabytes) by typing `gc()` at the R prompt. Note that following `gcinfo(TRUE)`, automatic garbage collection always prints memory use statistics. Maxima will never be reduced below the current values for triggering garbage collection, and attempts to do so will be silently ignored.

When using `read.table`, the memory requirements are in fact higher than anticipated, because the file is first read in as one long string which is then split again. Use `scan` if possible in case you run out of memory when reading in a large table.

### Value

(`mem.limits`) an integer vector giving the current settings of the maxima, possibly `NA`.

### Note

For backwards compatibility, options `--nsize` and `--vsize` are equivalent to `--min-nsize` and `--min-vsize`.

### See Also

`gc` for information on the garbage collector, `memory.profile` for profiling the usage of cons cells.

### Examples

    # Start R with 10MB of heap memory and 500k cons cells, limit to
    # 100Mb and 1M cells

    ## Unix
    R --min-vsize=10M --max-vsize=100M --min-nsize=500k --max-nsize=1M

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