Error when executing MATLAB app methods via parfeval and BackgroundWorker pool.

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I try to execute some method from my app asynchronously in the background. The goal is to be able to cancel it if it gets stuck and to execute suitable function-specific failure reaction.
function MainFunc(app)
%modify some local app properties and access external APIs
% Button pushed function: StartExecButton
function StartExecButtonPushed(app, event)
FunHandle = parfeval(backgroundPool,@MainFunc,0,app);
if strcmp(FunHandle.State,'running')
app.InfoTxt=[app.InfoTxt;{'WatchDog: Main Function took too long and was aborted.'}];
cancel(FunHandle); %just as a safety measure
if app.MainSuccess
app.InfoTxt=[app.InfoTxt;{'WatchDog: Main Function finished in time with success.'}];
app.InfoTxt=[app.InfoTxt;{'WatchDog: Main Function finished in time without success.'}];
When the function is called via parfeval I observe a failure message "parallel:threadpool:NonConcurrentLibrary / Use of library hg is not supported on a thread-based worker. Use alternatives supported on the background pool."
Does that mean that background pool is generally not useable with MATLAB apps, or am I just using it wrongly?
If usage with apps is not supported, is there any other parallel / concurrent execution framework that can be used with apps?

Accepted Answer

Sean de Wolski
Sean de Wolski on 11 Nov 2021
MainFunc should be an external function you call and not an app class method. The app can update itself with the results of the main func computation. If you need this to happen while MainFunc is still running, you can use a DataQueue to pass the data back to the app client so it can self-update.
Sean de Wolski
Sean de Wolski on 11 Nov 2021
You may want to consider using Stateflow for MATLAB to manage this. A simple state chart that transitions when the future either, finishes, errors, or it polls at some beat and can cancel it after a delay.

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More Answers (1)

Raymond Norris
Raymond Norris on 11 Nov 2021
Do you have the Parallel Computing Toolbox? If so, try using a process-based pool (i.e., 'local') instead of a backgroundPool. For instance
p = gcp('nocreate');
if isempty(p)
p = parpool('local',1);
FunHandle = parfeval(p,@MainFunc,0,app);
  1 Comment
Lionel Pöffel
Lionel Pöffel on 11 Nov 2021
Does not seem to work. The MainFunc seems to be unable to access app properties.
Either I get failure messages à la "MATLAB:emptyObjectDotAssignment" although the app property in question gets assigned a non-empty value immediately prior to calling
FunHandle = parfeval(p,@MainFunc,0,app);
Or (if I comment out those assignments) the function still behaves as if certain other app properties had not been initialized properly (which, however, they have)

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