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Is CPU energy measurable here?

Source: R/compute_footprint.R
raplok.Rd

TRUE when the operating system exposes readable RAPL (Running Average Power Limit) energy counters for at least one CPU package: Linux with the intel_rapl powercap driver (Intel and, since kernel 5.8, AMD), with read permission on energy_uj. On most systems since Linux 5.10 that file is readable by root only, so FALSE is the common answer for an ordinary user, and co2fp then falls back to its model.

Usage

raplok(rapldir = "/sys/class/powercap")

Arguments

rapldir

Character scalar, the powercap directory; default "/sys/class/powercap", the Linux location. Another path is useful for testing against a copy of the directory tree.

Value

A logical scalar: TRUE when every CPU-package energy counter under rapldir is readable, FALSE otherwise (including when the directory does not exist).

Details

A domain counts when it is a directory named intel-rapl:N (the intel-rapl:N:M subdomains are parts of a package and would count the same energy twice) whose name file starts with "package" and whose energy_uj file holds a number. Every such domain must be readable: if any is not, the answer is FALSE. Only files under rapldir are read; nothing is written. On macOS and Windows there is no such directory and the answer is FALSE. Errors when rapldir is not a single non-missing string.

See also

co2fp

Examples

raplok()
#> [1] FALSE

# a fake powercap tree with one readable package domain (Linux names the
# domain "intel-rapl:0"; a colon is not allowed in a Windows file name)
if (.Platform$OS.type != "windows") {
  d <- file.path(tempfile(), "intel-rapl:0")
  dir.create(d, recursive = TRUE)
  writeLines("package-0", file.path(d, "name"))
  writeLines("123456789", file.path(d, "energy_uj"))
  raplok(dirname(d))
}
#> [1] TRUE

# a folder that does not exist is simply FALSE; a non-path is an error
raplok(file.path(tempdir(), "no-such-dir"))
#> [1] FALSE
try(raplok(NA_character_))
#> Error : `rapldir` must be a single directory path