S Thread API - Evaluator Manager Query Functions

Title: Evaluator Manager Query Functions isAlive() - checks to see if each of the thread objects are still "active" and potentially available for performing tasks. Returns F for each thread referenced if it has been started and has exited (normally or abnormally) or has been cancelled by another thread (even if it is not yet dead), and T if the thread is still executing, even if it has no tasks to perform but is accepting tasks. NULL is returned if no such thread (or threadGroup) exists. isBlocked tests whether each of the thread objects are blocked waiting for a lock. isCancelled() - tests whether each of the thread objects are considered cancelled (not simply in cancel pending mode). Returns T if the thread is in cancelled mode (not just a cancel request pending) and F otherwise. NULL is returned if the thread doesn't exist. isIdle() - determines whether the task queues are emptry but active for each of the thread objects. Returns T for each thread that has an empty task queue and is not evaluating a task and F for threads that doing something. NULL is returned if the thread doesn't exist. isSuspended() - tests each thread determining if it is in suspended mode. Returns T for each thread that is currently suspended and F for threads that are still alive. NULL is returned if the thread doesn't exist. isFinished() - tests each thread to determine if it is considered terminated. This is the opposite of isAlive(), I think. Returns T for each thread that has completed the tasks supplied and F if it is still executing. NULL is returned if the thread doesn't exist. valueOf() - returns the exit value for each of supplied thread objects. threadOf() - for each object supplied, the associated thread is returned. This is most useful for threadLock objects so as to be able to determine which thread holds the lock at the time of evaluation of this expression. dbOf() - returns the database or frame into which the toplevel assignments will be comitted for each of the supplied threads. searchPathOf() - returns the search path as a vector of databases and frames for each of the supplied threads.
Usage: F(...) where F is one of the functions above
Arguments: There are two categories of functions in the above list based on the type of arguments on which they operate. These categories are threadOf() and all others. threadOf() ...: any object that can be associated with a thread from the global evaluator. This is primarily intended for threadLock objects and the return value is the thread that currently holds the lock, if any. This does operate on variables, but could be extended to do so. The basic idea is that we have a generic function, getThreadOf which is called for each of the objects passed. Other functions ...: objects or lists or vectors of class thread or threadGroup. Each object is unravelled into elements of these two classes and each element is processed individually. The return value is a list of the same length as the unravelled list. Could operate on threadGroup objects individually.
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Examples: # exit if the standard reader is dead if(!isAlive(main.stdin.thread)) q() if(threadOf(lock)!= self()) getLock(lock) if(isAlive(tA)) suspend(tA) # find an idle thread and send it the next task. group = threadGroup() i = min((1:length(group))[isIdle(group)]) sendTask(Quote(next.expression), group[i])
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# exit if the standard reader is dead if(!isAlive(main.stdin.thread)) q()
if(threadOf(lock)!= self()) getLock(lock)
if(isAlive(tA)) suspend(tA)
# find an idle thread and send it the next task. group = threadGroup() i = min((1:length(group))[isIdle(group)]) sendTask(Quote(next.expression), group[i])

Last modified: Mon Apr 7 20:29:26 PDT 1997

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