inst/testme/test-cancel.R

In future: Unified Parallel and Distributed Processing in R for Everyone

#' @tags cancel
#' @tags detritus-files
#' @tags detritus-connections
#' @tags sequential multisession multicore

library(future)
options(future.debug = FALSE)

strategies <- supportedStrategies()
#strategies <- setdiff(strategies, "sequential")

for (strategy in strategies) {
  message(sprintf("plan('%s') ...", strategy))
  plan(strategy)

  n0 <- nbrOfFreeWorkers()
  message("  Number of free workers: ", n0)

  message("  Create a future")
  f <- future({ Sys.sleep(1.0); 42 })
  stopifnot(
     f[["state"]] == "running" ||
    (f[["state"]] == "finished" && inherits(f, "SequentialFuture"))
  )
  stopifnot(
    !resolved(f) || 
    (resolved(f) && f[["state"]] == "finished")
  )

  message("  Cancel future, which also interrupts the future, if supported")
  f <- cancel(f)
  stopifnot({
     f[["state"]] %in% c("canceled", "interrupted") ||
    (f[["state"]] == "finished" && inherits(f, "SequentialFuture"))
  })
  
  n <- nbrOfFreeWorkers()
  message("  Number of free workers (after cancel + interupt): ", n)
  
  message("  Check if canceled + interrupted future is resolved")
  f <- resolve(f)
  stopifnot(resolved(f))
  stopifnot({
     f[["state"]] %in% c("canceled", "interrupted") ||
    (f[["state"]] == "finished" && inherits(f, "SequentialFuture"))
  })
  
  n <- nbrOfFreeWorkers()
  message("  Number of free workers (after resolve): ", n)
  
  message("  Force collect of canceled future (to free up worker)")
  ## Force collection of the future
  r <- tryCatch(result(f), error = identity)
  n <- nbrOfFreeWorkers()
  message("Number of free workers (after result): ", n)
  stopifnot(n == n0)

  message("  And cancel the same future multiple times")
  for (kk in 1:10) {
    f <- cancel(f)
  }

  message("  Create another future")
  ## Create another future
  f <- future(42)
  v <- value(f)
  n <- nbrOfFreeWorkers()
  message("  Number of free workers (after result): ", n)
  stopifnot(n == n0)

  message(sprintf("plan('%s') .. done", strategy))
}

message("Shut down future backend")
plan(sequential)
gc()