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#
# Copyright (c) Microsoft. All rights reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
#' @include foreach.R
NULL
# this explicitly registers a sequential backend for do and dopar.
#' @title registerDoSEQ
#' @description
#' The `registerDoSEQ` function is used to explicitly register
#' a sequential parallel backend with the foreach package.
#' This will prevent a warning message from being issued if the
#' `%dopar%` function is called and no parallel backend has
#' been registered.
#'
#' @seealso
#' [`doParallel::registerDoParallel`]
#' @examples
#' # specify that %dopar% should run sequentially
#' registerDoSEQ()
#' @keywords utilities
#' @export
registerDoSEQ <- function() {
setDoPar(doSEQ, NULL, info)
setDoSeq(doSEQ, NULL, info)
}
# passed to setDoPar via registerDoSEQ, and called by getDoSeqWorkers, etc
info <- function(data, item) {
switch(item,
workers=1L,
name='doSEQ',
version=packageDescription('foreach', fields='Version'),
NULL)
}
#' @export
#' @rdname foreach
'%do%' <- function(obj, ex) {
e <- getDoSeq()
# set a marker that we are calling the iterator from %do%, rather than %dopar%
# this is required to let %dopar% eval its expr in a local env
environment(e$fun) <- new.env(parent=environment(e$fun))
environment(e$fun)$.foreach_do <- TRUE
e$fun(obj, substitute(ex), parent.frame(), e$data)
}
#' @export
#' @rdname foreach
'%dopar%' <- function(obj, ex) {
e <- getDoPar()
e$fun(obj, substitute(ex), parent.frame(), e$data)
}
comp <- if (getRversion() < "2.13.0") {
function(expr, ...) expr
} else {
compiler::compile
}
doSEQ <- function(obj, expr, envir, data) {
# check for a marker that this is called from %do%, not %dopar%
# if the marker does not exist, we are in a %dopar% call
if(is.null(parent.env(environment())$.foreach_do) &&
getOption("foreachDoparLocal"))
envir <- new.env(parent=envir)
# note that the "data" argument isn't used
if (!inherits(obj, 'foreach'))
stop('obj must be a foreach object')
it <- iter(obj)
accumulator <- makeAccum(it)
for (p in obj$packages)
library(p, character.only=TRUE)
# compile the expression if we're using R 2.13.0 or greater
xpr <- comp(expr, env=envir, options=list(suppressUndefined=TRUE))
i <- 1
tryCatch({
repeat {
# get the next set of arguments
args <- nextElem(it)
if (obj$verbose) {
cat(sprintf('evaluation # %d:\n', i))
print(args)
}
# assign arguments to local environment
for (a in names(args))
assign(a, args[[a]], pos=envir, inherits=FALSE)
# evaluate the expression
r <- tryCatch(eval(xpr, envir=envir), error=function(e) e)
if (obj$verbose) {
cat('result of evaluating expression:\n')
print(r)
}
# process the results
tryCatch(accumulator(list(r), i), error=function(e) {
cat('error calling combine function:\n')
print(e)
NULL
})
i <- i + 1
}
},
error=function(e) {
if (!identical(conditionMessage(e), 'StopIteration'))
stop(simpleError(conditionMessage(e), expr))
})
errorValue <- getErrorValue(it)
errorIndex <- getErrorIndex(it)
if (identical(obj$errorHandling, 'stop') && !is.null(errorValue)) {
msg <- sprintf('task %d failed - "%s"', errorIndex,
conditionMessage(errorValue))
stop(simpleError(msg, call=expr))
} else {
getResult(it)
}
}
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