Inter-process locks and counters
Functions documented on this page enable locks and counters between processes on the same computer.
Use ipcid() to generate a unique mutex or counter identifier. A
mutex or counter with the same id, including those in different
processes, share the same state.
ipcremove() removes external state associated with mutex or
counters created with id.
ipclock() blocks until the lock is
obtained. ipctrylock() tries to obtain the lock, returning
immediately if it is not available. ipcunlock() releases the
lock. ipclocked() queries the lock to determine whether it is
currently held.
ipcyield() returns the current counter, and increments the
value for subsequent calls. ipcvalue() returns the current
counter without incrementing. ipcreset() sets the counter to
n, such that the next call to ipcyield() or
ipcvalue() returns n.
## Utilities ipcid(id) ipcremove(id) ## Locks ipclock(id) ipctrylock(id) ipcunlock(id) ipclocked(id) ## Counters ipcyield(id) ipcvalue(id) ipcreset(id, n = 1)
id |
character(1) identifier string for mutex or
counter. |
n |
integer(1) value from which |
Locks:
ipclock() creates a named lock, returning TRUE
on success.
trylock() returns TRUE if the lock is
obtained, FALSE otherwise.
ipcunlock() returns TRUE on success,
FALSE (e.g., because there is nothing to unlock)
otherwise.
ipclocked() returns TRUE when id is locked, and
FALSE otherwise.
Counters:
ipcyield() returns an integer(1) value representing the next
number in sequence. The first value returned is 1.
ipcvalue() returns the value to be returned by the next call to
ipcyield(), without incrementing the counter. If the counter is
no longer available, ipcyield() returns NA.
ipcreset() returns n, invisibly.
Utilities:
ipcid() returns a character(1) unique identifier, with
id (if not missing) prepended.
ipcremove() returns (invisibly) TRUE if external
resources were released or FALSE if not (e.g., because the
resources has already been released).
ipcid()
## Locks
id <- ipcid()
ipclock(id)
ipctrylock(id)
ipcunlock(id)
ipctrylock(id)
ipclocked(id)
ipcremove(id)
id <- ipcid()
system.time({
## about 1s, .2s for each process instead of .2s if no lock
result <- bplapply(1:2, function(i, id) {
BiocParallel::ipclock(id)
Sys.sleep(.2)
time <- Sys.time()
BiocParallel::ipcunlock(id)
time
}, id)
})
ipcremove(id)
diff(sort(unlist(result, use.names=FALSE)))
## Counters
id <- ipcid()
ipcyield(id)
ipcyield(id)
ipcvalue(id)
ipcyield(id)
ipcreset(id, 10)
ipcvalue(id)
ipcyield(id)
ipcremove(id)
id <- ipcid()
result <- bplapply(1:2, function(i, id) {
BiocParallel::ipcyield(id)
}, id)
ipcremove(id)
sort(unlist(result, use.names=FALSE))Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.