init.R

## init.R: Startup
##
## Copyright (C)  2023-2026  Dirk Eddelbuettel
##
## This file is part of RcppArmadillo.
##
## RcppArmadillo is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 2 of the License, or
## (at your option) any later version.
##
## RcppArmadillo is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with RcppArmadillo.  If not, see <http://www.gnu.org/licenses/>.

.pkgenv <- new.env(parent=emptyenv())

.onLoad <- function(libname, pkgname) {					# nocov start
    ## simple fallback: 'Ncpus' (if set) or else all cpus seen by OpenMP
    ncores <- getOption("Ncpus", armadillo_get_number_of_omp_threads())
    ## consider OMP_THREAD_LIMIT (cf Writing R Extensions), gets NA if envvar unset
    ompcores <- as.integer(Sys.getenv("OMP_THREAD_LIMIT"))
    ## keep the smaller value, omitting NA
    ncores <- min(na.omit(c(ncores, ompcores)))
    .pkgenv[["omp_threads"]] <- ncores
    armadillo_throttle_cores(ncores)
}

.onAttach <- function(libname, pkgname) {
    if (interactive()) {
        packageStartupMessage("RcppArmadillo ",
                              packageDescription("RcppArmadillo", fields="Version"),
                              " using ", .pkgenv[["omp_threads"]], " cores. See ",
                              "'help(\"RcppArmadillo-package\")' for details.")
    }
}

##' Throttle (or Reset) (Rcpp)Armadillo to Two Cores
##'
##' Helper functions to throttle use of cores by RcppArmadillo-internal
##' code on systems with OpenMP. On package load, the initial value is
##' saved and used to reset the value.
##' @param n Integer value of desired cores, default is two
armadillo_throttle_cores <- function(n = 2) {
    armadillo_set_number_of_omp_threads(n)
}

##' @rdname armadillo_throttle_cores
armadillo_reset_cores <- function() {
    n <- .pkgenv[["omp_threads"]]
    armadillo_set_number_of_omp_threads(n)
}														# nocov end