Terminating the external program with system command.

Hello,

I am running XFOIL inside the fmincon function. However, xfoil is unstable in some cases. It freezes and MATLAB hangs there forever.

I am using the following code to do timer and taskkill trick, but it does not work:

% Create a timer object
t = timer('StartDelay', 4);
cmd_1 = sprintf(['cd %s && taskkill /IM /F xfoil.exe'],wd);
t.TimerFcn = @(~,~) system(cmd_1);

% Start the timer
start(t);

% execute xfoil
cmd_2 = sprintf(['cd %s && xfoil.exe < "%skill_xfoil_test.inp" > "%skill_xfoil_test.out"'],wd, [wd filesep folder filesep], [wd filesep folder filesep]);
[status,result] = system(cmd_2);

% Stop and delete the timer object
stop(t);
delete(t);

It seems like MATLAB finishes the execution of XFOIL first and then try to kill it.

Does anyone know how to fix this? I appriciate any help.

Thank you!

Answer 1

[Ayush]

Here is the possible workaround to ensure MATLAB terminates XFOIL properly:

• Use ‘system’ command with appropriate options:

system('xfoil.exe', '-wait'); 

using ‘-wait’ option MATLAB will not attempt to kill XFOIL until it has finished executing.

Read further on system command: https://in.mathworks.com/help/matlab/ref/system.html

• Timeout mechanism with Tic Toc:

timeout = 60; % Timeout value in seconds 
t = tic; 
while toc(t) < timeout 
    % Check if XFOIL has completed 
    if xfoilCompleted() 
        break; 
    end 
    % Pause for a short duration before checking again 
    pause(1); 
end 

In this example, the script waits for XFOIL to complete for a maximum of 60 seconds. If XFOIL has not completed within the timeout period, the script can proceed with the next steps.

Read about Tic and Toc:

1. https://in.mathworks.com/help/matlab/ref/tic.html
2. https://in.mathworks.com/help/matlab/ref/toc.html

Answer 2

[Walter Roberson]

On Windows systems, there is an alternate mechanism.

If you use the .NET System.Diagnostics.Process interface, you can start processes running asynchronously, with MATLAB still running. You can have timers and detect whether the process finished, and if not then you can use the S.D.P interface to cancel the process. You would not use system() to start the process and you would not use system() to terminate the process if need be.

This interface is not supported on Mac or Linux.

(On the other hand, MacOS and Linux do not use taskmgr ...)