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#' Thread options for RcppParallel
#'
#' Set thread options (number of threads to use for task scheduling and stack
#' size per-thread) for RcppParallel.
#'
#' RcppParallel is automatically initialized with the default number of threads
#' and thread stack size when it loads. You can call `setThreadOptions()` at
#' any time to change the defaults.
#'
#' The `parallelFor()` and `parallelReduce()` also accept `numThreads` as
#' an argument, if you'd like to control the number of threads specifically
#' to be made available for a particular parallel function call. Note that
#' this value is advisory, and TBB may choose a smaller number of threads
#' if the number of requested threads cannot be honored on the system.
#'
#' @aliases setThreadOptions defaultNumThreads
#'
#' @param numThreads
#' Number of threads to use for task scheduling. Call `defaultNumThreads()`
#' to determine the the default value used for "auto".
#'
#' @param stackSize
#' Stack size (in bytes) to use for worker threads. The
#' default used for "auto" is 2MB on 32-bit systems and 4MB on 64-bit systems
#' (note that this parameter has no effect on Windows).
#'
#' @return
#' `defaultNumThreads()` returns the default number of threads used by
#' RcppParallel, if another value isn't specified either via
#' `setThreadOptions()` or explicitly in calls to `parallelFor()` and
#' `parallelReduce()`.
#'
#' @examples
#'
#' \dontrun{
#' library(RcppParallel)
#' setThreadOptions(numThreads = 4)
#' defaultNumThreads()
#' }
#'
#' @export setThreadOptions
setThreadOptions <- function(numThreads = "auto",
stackSize = "auto")
{
# validate and resolve numThreads
if (identical(numThreads, "auto"))
numThreads <- -1L
else if (!is.numeric(numThreads))
stop("numThreads must be an integer")
else
numThreads <- as.integer(numThreads)
# validate and resolve stackSize
if (identical(stackSize, "auto"))
stackSize <- 0L
else if (!is.numeric(stackSize))
stop("stackSize must be an integer")
else
stackSize <- as.integer(stackSize)
# set RCPP_PARALLEL_NUM_THREADS
if (numThreads == -1L)
Sys.unsetenv("RCPP_PARALLEL_NUM_THREADS")
else
Sys.setenv(RCPP_PARALLEL_NUM_THREADS = numThreads)
# set RCPP_PARALLEL_STACK_SIZE
if (stackSize == 0L)
Sys.unsetenv("RCPP_PARALLEL_STACK_SIZE")
else
Sys.setenv(RCPP_PARALLEL_STACK_SIZE = stackSize)
}
#' @rdname setThreadOptions
#' @export
defaultNumThreads <- function() {
.Call("defaultNumThreads", PACKAGE = "RcppParallel")
}
isUsingTbb <- function() {
backend <- Sys.getenv("RCPP_PARALLEL_BACKEND", "tbb")
identical(backend, "tbb")
}
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