DEPRECATION: Deprecated plan(multiprocess, ...) now equals plan(seque…

…ntial); same for multiprocess() -> sequential() [#546]

DESCRIPTION

@@ -1,5 +1,5 @@
 Package: future
-Version: 1.30.0-9016
+Version: 1.30.0-9017
 Title: Unified Parallel and Distributed Processing in R for Everyone
 Imports:
     digest,

NEWS.md

@@ -21,6 +21,9 @@
 
  * Remove defunct functions `transparent()` and `TransparentFuture()`.
 
+ * Deprecated `plan(multiprocess, ...)` now equals `plan(sequential)`,
+   while still producing one warning each time a future is created.
+
 
 # Version 1.30.0 [2022-12-15]
 

R/multiprocess.R

@@ -1,49 +1,30 @@
 #' Create a multiprocess future whose value will be resolved asynchronously using multicore or a multisession evaluation
 #'
-#' A multiprocess future is a future that uses [multicore] evaluation
-#' if supported, otherwise it uses [multisession] evaluation.
-#' Regardless, its _value is computed and resolved in
-#' parallel in another process_.\cr
-#' \cr
 #' **WARNING: The 'multiprocess' future plan is deprecated.
 #' Instead, explicitly specify 'multisession' or 'multicore'.  The former works
 #' everywhere and is the recommended one between the two. _Forked processing_,
 #' which 'multicore' uses, is unstable in various environment and setups.
-#' The 'multiprocess' alias is therefore being phased out.**
+#' The 'multiprocess' alias is therefore being phased out, and is now
+#' equal to using 'sequential' (sic!)**
 #'
 #' @inheritParams ClusterFuture-class
 #' @inheritParams future
 #' @inheritParams Future-class
 #' 
-#' @param workers A positive numeric scalar or a function specifying the
-#' maximum number of parallel futures that can be active at the same time
-#' before blocking.
-#' If a function, it is called without arguments _when the future
-#' is created_ and its value is used to configure the workers.
-#' The function should return a numeric scalar.
+#' @param workers Ignored in **future** (>= 1.31.0).
 #' 
 #' @param \dots Additional arguments passed to [Future()].
 #'
 #' @return
-#' A [MultiprocessFuture] implemented as either a
-#' [MulticoreFuture] or a [MultisessionFuture].
-#'
-#' @example incl/multiprocess.R
-#'
-#' @seealso
-#' Internally [multicore()] and [multisession()]
-#' are used.
+#' A [SequentialFuture] (sic!) since **future** 1.31.0.
 #'
 #' @keywords internal
 #'
 #' @export
 multiprocess <- function(..., workers = availableCores(), envir = parent.frame()) {
-  if (!is.element("multiprocess", getOption("future.deprecated.ignore"))) {
-    .Deprecated(msg = sprintf("Detected creation of a 'multiprocess' future. Strategy 'multiprocess' is deprecated in future (>= 1.20.0) [2020-10-30]. Instead, explicitly specify either 'multisession' (recommended) or 'multicore'. In the current R session, 'multiprocess' equals '%s'.", if (supportsMulticore()) "multicore" else "multisession"))
-  }
-
-  fun <- if (supportsMulticore(warn = TRUE)) multicore else multisession
-  fun(..., workers = workers, envir = envir)
+  .Deprecated(msg = sprintf("Detected creation of a 'multiprocess' future. Strategy 'multiprocess' is deprecated in future (>= 1.20.0) [2020-10-30]. Instead, explicitly specify either 'multisession' (recommended) or 'multicore'. Starting with future 1.31.0 [2023-01-??], 'multiprocess' is the same as 'sequential'."))
+  sequential(..., envir = envir)
 }
-class(multiprocess) <- c("multiprocess", "future", "function")
-attr(multiprocess, "init") <- NA ## Set to FALSE/TRUE in .onLoad()
+class(multiprocess) <- c("sequential", "uniprocess", "future", "function")
+## future (> 1.30.0): 'multiprocess' always resolves to 'sequential'
+attr(multiprocess, "init") <- FALSE

R/zzz.R

@@ -17,12 +17,6 @@
 
   ## Set future options based on environment variables
   update_package_options(debug = debug)
-
-  ## Does multiprocess resolve to multisession? If so, then
-  ## plan(multiprocess) should initiate the workers.
-  if (is.na(attr(multiprocess, "init", exact = TRUE))) {
-    attr(multiprocess, "init") <<- !supportsMulticore()
-  }
 
   ## Initiate the R session UUID, which will also set/update
   ## .GlobalEnv$.Random.seed.

R/zzz.plan.R

@@ -175,7 +175,7 @@ plan <- local({
   }
 
   warn_about_multiprocess <- function(stack) {
-    warn_about_deprecated(stack, strategy = "multiprocess", fmtstr = sprintf("Strategy '%%s' is %%s in future (>= 1.20.0) [2020-10-30]. Instead, explicitly specify either 'multisession' (recommended) or 'multicore'. In the current R session, 'multiprocess' equals '%s'.", if (supportsMulticore()) "multicore" else "multisession"))
+    warn_about_deprecated(stack, strategy = "multiprocess", fmtstr = sprintf("Strategy '%%s' is %%s in future (>= 1.20.0) [2020-10-30]. Instead, explicitly specify either 'multisession' (recommended) or 'multicore'. Starting with future 1.31.0 [2023-01-??], 'multiprocess' is the same as 'sequential'."))
   }
 
   warn_about_remote <- function(stack) {
@@ -484,8 +484,7 @@ plan <- local({
 
 
 supportedStrategies <- function(strategies = c("sequential", "multicore",
-                                               "multisession", "multiprocess",
-                                               "cluster")) {
+                                               "multisession", "cluster")) {
   if (!supportsMulticore()) strategies <- setdiff(strategies, "multicore")
   strategies
 }

tests/multiprocess.R

@@ -16,7 +16,7 @@ for (cores in 1:availCores) {
     42L
   })
   print(f)
-  stopifnot(inherits(f, "MultiprocessFuture") || inherits(f, "SequentialFuture"))
+  stopifnot(inherits(f, "SequentialFuture"))
 
   print(resolved(f))
   y <- value(f)