seize: Seize/Release Resources

In simmer: Discrete-Event Simulation for R

Seize/Release Resources

Description

Activities for seizing/releasing a resource, by name or a previously selected one. Resources must be defined in the simulation environment (see add_resource).

Usage

seize(.trj, resource, amount = 1, continue = NULL, post.seize = NULL,
  reject = NULL, ..., tag)

seize_selected(.trj, amount = 1, id = 0, continue = NULL,
  post.seize = NULL, reject = NULL, ..., tag)

release(.trj, resource, amount = 1, ..., tag)

release_selected(.trj, amount = 1, id = 0, ..., tag)

release_all(.trj, resource, ..., tag)

release_selected_all(.trj, id = 0, ..., tag)

Arguments

.trj	the trajectory object.
resource	the name of the resource.
amount	the amount to seize/release, accepts either a numeric or a callable object (a function) which must return a numeric.
continue	a boolean (if post.seize OR reject is defined) or a pair of booleans (if post.seize AND reject are defined; if only one value is provided, it will be recycled) to indicate whether these subtrajectories should continue to the next activity in the main trajectory.
post.seize	an optional trajectory object which will be followed after a successful seize.
reject	an optional trajectory object which will be followed if the arrival is rejected (dropped).
...	unused.
tag	activity tag name to perform named rollbacks (see rollback) or just to better identify your activities.
id	selection identifier for nested usage.

Details

Rejection happens when a resource is at full capacity and there is no room in the queue (either because there is a finite queue_size and it is full, or because queue_size=0 and thus it is disabled). In those cases, the reject parameter defines a fallback trajectory. Note, however, that, if the arrival is accepted (either in the queue or in the server) and then it is dropped afterwards due to preemption or resource shrinkage, then this trajectory will not be executed. Instead, see handle_unfinished for another, more general, method for handling all kinds of unfinished arrivals.

Value

Returns the trajectory object.

See Also

select, set_capacity, set_queue_size, set_capacity_selected, set_queue_size_selected

Examples

## simple seize, delay, then release
traj <- trajectory() %>%
  seize("doctor", 1) %>%
  timeout(3) %>%
  release("doctor", 1)

simmer() %>%
  add_resource("doctor", capacity=1) %>%
  add_generator("patient", traj, at(0, 1)) %>%
  run() %>%
  get_mon_resources()

## arrival rejection (no space left in the queue)
traj <- trajectory() %>%
  log_("arriving...") %>%
  seize("doctor", 1) %>%
  # the second patient won't reach this point
  log_("doctor seized") %>%
  timeout(5) %>%
  release("doctor", 1)

simmer() %>%
  add_resource("doctor", capacity=1, queue_size=0) %>%
  add_generator("patient", traj, at(0, 1)) %>%
  run() %>% invisible

## capturing rejection to retry
traj <- trajectory() %>%
  log_("arriving...") %>%
  seize(
    "doctor", 1, continue = FALSE,
    reject = trajectory() %>%
      log_("rejected!") %>%
      # go for a walk and try again
      timeout(2) %>%
      log_("retrying...") %>%
      rollback(amount = 4, times = Inf)) %>%
  # the second patient will reach this point after a couple of walks
  log_("doctor seized") %>%
  timeout(5) %>%
  release("doctor", 1) %>%
  log_("leaving")

simmer() %>%
  add_resource("doctor", capacity=1, queue_size=0) %>%
  add_generator("patient", traj, at(0, 1)) %>%
  run() %>% invisible

## combining post.seize and reject
traj <- trajectory() %>%
  log_("arriving...") %>%
  seize(
    "doctor", 1, continue = c(TRUE, TRUE),
    post.seize = trajectory("admitted patient") %>%
      log_("admitted") %>%
      timeout(5) %>%
      release("doctor", 1),
    reject = trajectory("rejected patient") %>%
      log_("rejected!") %>%
      seize("nurse", 1) %>%
      timeout(2) %>%
      release("nurse", 1)) %>%
  # both patients will reach this point, as continue = c(TRUE, TRUE)
  timeout(10) %>%
  log_("leaving...")

simmer() %>%
  add_resource("doctor", capacity=1, queue_size=0) %>%
  add_resource("nurse", capacity=10, queue_size=0) %>%
  add_generator("patient", traj, at(0, 1)) %>%
  run() %>% invisible

simmer documentation built on Sept. 28, 2024, 1:07 a.m.