Alert sound/mail for warning me if the program runs overtime.

Is there any way to notify me if a function I call doesn't return a result in 20seconds. (I am not allowed to make any change to the function. I can change only the main function which calls the function.)

Is it possible to run two codes parallel; one the function and the other a timer.

Thank you.

Answer 1

[Walter Roberson]

Yes, barely. You can use parfeval() to start the routine. After 20 seconds, check the status of the "future" that it returns; if it has not finished then cancel the future, and otherwise collect its result.

Note: any routine you run this way will not have access to graphics.

Answer 2

[dbmn]

Another option is to use the timer function. But it is kind of tricky and not as nice.

clear all; close all; clc

% Initialize variables
finished_1 = false;
finished_2 = false;

% Run first Function
disp('FUNCTION 1')
start(timer('TimerFcn',{@checkfun, 'finished_1'},'StartDelay',1.5));
finished_1 = myfun1();

pause(1)

% Run second Function
start(timer('TimerFcn',{@checkfun, 'finished_2'},'StartDelay',1.5));
disp('FUNCTION 2')
finished_2 = myfun2();

%%Function declarations

function [finished] = myfun1()
    pause(1);
    finished = true;
end

function [finished] = myfun2()
    pause(2);
    finished = true;
end

function [] = checkfun(~, ~, varname)
    finished = evalin('base',varname); % if you pass a variable it will take one without delay
    if finished
        disp('finished')
    else
        disp('not finished')
    end
end

[Walter Roberson]

The above will generally work to detect the call not returning in the appropriate amount of time, but it cannot cancel execution of the call if it goes on too long.

Also, when timer functions get run depends on the version in use. In recent versions, the documented rule (somewhere or other) is that timers can interrupt between any two lines of MATLAB source. But notice that calls into hard-coded routines or third-party routines are not MATLAB routines; in particular, operators such as \ or eig() will not be interrupted by timers.

I no longer recall the older rules about when timer interrupts could occur; I don't think it was really documented. I think I had decided it could not interrupt inside a control block (if, while, switch) of the routine that was executing.

[dbmn]

You are right. Thank you for clarifying the points of interuptions of the timer function - i didn't know that.

There is one way to cancel the execution if it goes on for too long - but it rather nasty by introducing try/catch statements with exceptions.

finished_1 = false;
try 
    start(timer('TimerFcn',{@checkfun, 'finished_1'},'StartDelay',1.5));
    finished_1 = myfun1();
catch 
    % continue
end

while trowing an exception in the checkfun of the timer, if the execution takes too long.

function [] = checkfun(~, ~, varname)
    finished = evalin('base',varname); 
    if ~ finished
        error('my special error')
    end
end

not nice, but lets you stop the current execution and resume with the rest of the code

[Walter Roberson]

The timer lives in a different execution context, just like graphics interrupts do. You cannot catch errors generated in callbacks by any routine outside the callback.