detectCores {parallel}

R Documentation

Detect the Number of CPU Cores

Description

Attempt to detect the number of CPU cores on the current host.

Usage

detectCores(all.tests = FALSE, logical = FALSE)

Arguments

all.tests	Logical: if true apply all known tests.
logical	Logical: if possible, use the number of physical CPUs/cores (if FALSE) or logical CPUs (if TRUE).

Details

This attempts to detect the number of CPU cores in the current machine.

It has methods to do so for Linux, OS X, FreeBSD, Solaris, Irix and Windows. detectCores(TRUE) could be tried on other Unix-alike systems.

Value

An integer, NA if the answer is unknown.

Exactly what this represents is OS-dependent: where possible by default it represents physical cores and not logical (e.g. hyperthreaded) CPUs.

On Windows the default is the number of logical CPUs.

Currently logical makes a difference on Sparc Solaris: there logical = FALSE returns the number of physical cores and logical = TRUE returns the number of available hardware threads. (Some Sparc CPUs which do have multiple cores per CPU, others have multiple threads per core and some have both.) For example, the UltraSparc T2 CPU in the CRAN check server is a single physical CPU with 8 cores, and each core supports 8 hardware threads. So detectCores(logical = FALSE) returns 8, and detectCores(logical = TRUE) returns 64.

Where virtual machines are in use, one would hope that the result represents the number of CPUs available (or potentially available) to that particular VM.

Author(s)

Simon Urbanek and Brian Ripley

Examples

detectCores()
detectCores(logical = TRUE)

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