I am using parallel computing toolbox. When my matlab code terminates due to exception/error while parallel worker is running (e.g. inside an infinite loop), I have to restart the pool via delete(gcp) and rerunning gcp. Otherwise the following runs always freeze. But restarting parallel pools takes too much time.
This does not happen when I manually cancel the future object cancel(futureObject) but I do no want to do this everytime program unexpectedly terminates.
I can cancel futureObject at the beginning of the matlab script but the object gets removed when I accidently do clear all and there is no way but I have to dodelete(gcp). Is there a way to cancel all futureobject automatically (even it is not in the base workspace anymore) everytime I restart matlab script?
I just decided to use try/catch block with cancel(futureObject) on the top-level of the script.
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My question might seem lame, but I am asking this out of curiosity. When we write a standalone java program , it gets executed and then gets terminated. But in socket programming, we create a while true loop, under which it continuously listens for a request. Is it only using while(true) that a server can be created, and if it does then will it not create a out of memory exception ?
With a while(true) loop there is no out of memory exception if you dont have memory leaks in your loop. If you would try to run endless with recursion, this would happen at some point due to the growing callstack.
If a program has to run endless (or until some condition, but not a fixed amount of operations), it needs an endless loop, sometimes it is called event-loop to sound more fancy, but most programs have it somewhere.
Technically you can also write for(;;) aswell, which can theoretically be better in unoptimized environments, because there is no condition that has to be checked, but most compilers will optimize the while(true)anyways.
For the use case of being able to abort parallel simulations with a MATLAB GUI, I would like to stop all scheduled simulations after the user pressed the Stop button.
All simulations are submitted at once using the parsim command, hence something like a callback to my GUI variables (App Designer) would be the most preferable solution.
Approaches I have considered but were not exactly providing a desirable solution:
The Simulation Manager provides the functionality to close simulations using its own interface. If I only had the code its Stop button executes...
parsim uses the Simulink.SimulationInput class as input to run simulations, allowing to modify the preSimFcn at the beginning of each simulation. I have not found a way to "skip" the simulation at its initialization phase apart from intentionally throwing an error so far.
Thank you for your help!
Update 1: Using the preSimFcn to set the the termination time equal to the start time drastically reduces simulation time. But since the first step still is computed there has to be a better solution.
simin = simin.setModelParameter('StopTime',get_param(mdl,'StartTime'))
Update 2: Intentionally throwing an error executing the preSimFcn, for example by setting it to
simin = simin.setModelParameter('SimulationCommand','stop')
provides the shortest termination times for me so far. Though, it requires catching and identifying the error in the ErrorMessageof the Simulink.SimulationOutput object. As this is exactly the "ugly" implementation I wanted to avoid, the issue is still active.
If you are using 17b or later, parsim provides an option to 'RunInBackground'. It returns an array of Future objects.
F = parsim(in, 'RunInBackground', 'on')
Please note that is only available for parallel simulations. The Simulink.Simulation.Future object F provides a cancel method which will terminate the simulation. You can use the fetchOutputs methods to fetch the output from the simulation.
F.cancel();
I know that an interrupt causes the OS to change a CPU from its current task and to run a kernel routine. I this case, the system has to save the current context of the process running on the CPU.
However, I would like to know whether or not a context switch occurs when any random process makes a system call.
I would like to know whether or not a context switch occurs when any random process makes a system call.
Not precisely. Recall that a process can only make a system call if it's currently running -- there's no need to make a context switch to a process that's already running.
If a process makes a blocking system call (e.g, sleep()), there will be a context switch to the next runnable process, since the current process is now sleeping. But that's another matter.
There are generally 2 ways to cause a content switch. (1) a timer interrupt invokes the scheduler that forcibly makes a context switch or (2) the process yields. Most operating systems have a number of system services that will cause the process to yield the CPU.
well I got your point. so, first I clear a very basic idea about system call.
when a process/program makes a syscall and interrupt the kernel to invoke syscall handler. TSS loads up Kernel stack and jump to syscall function table.
See It's actually same as running a different part of that program itself, the only major change is Kernel play a role here and that piece of code will be executed in ring 0.
now your question "what will happen if a context switch happen when a random process is making a syscall?"
well, nothing will happen. Things will work in same way as they were working earlier. Just instead of having normal address in TSS you will have address pointing to Kernel stack and SysCall function table address in that random process's TSS.
So I'm writing a mini timeout library in scala, it looks very similar to the code here: How do I get hold of exceptions thrown in a Scala Future?
The function I execute is either going to complete successfully, or block forever, so I need to make sure that on a timeout the executing thread is cancelled.
Thus my question is: On a timeout, does awaitAll terminate the underlying actor, or just let it keep running forever?
One alternative that I'm considering is to use the java Future library to do this as there is an explicit cancel() method one can call.
[Disclaimer - I'm new to Scala actors myself]
As I read it, scala.actors.Futures.awaitAll waits until the list of futures are all resolved OR until the timeout. It will not Future.cancel, Thread.interrupt, or otherwise attempt to terminate a Future; you get to come back later and wait some more.
The Future.cancel may be suitable, however be aware that your code may need to participate in effecting the cancel operation - it doesn't necessarily come for free. Future.cancel cancels a task that is scheduled, but not yet started. It interrupts a running thread [setting a flag that can be checked]... which may or may not acknowledge the interrupt. Review Thread.interrupt and Thread.isInterrupted(). Your long-running task would normally check to see if it's being interrupted (your code), and self-terminate. Various methods (i.e. Thread.sleep, Object.wait and others) respond to the interrupt by throwing InterruptedException. You need to review & understand that mechanism to ensure your code will meet your needs within those constraints. See this.
Is it possible in matlab to call a function when the program I'm running is idle? I don't want this to be a parallel process. Also, I would prefer a solution where I could pause and resume the function when the main program has to run again. Kind of like an interrupt in embedded systems, in my case the main program is the interrupt.
how would I do this?
you could use a timer object to start / stop the second function. see the matlab documentation. See also this mathworks blog entry.