MATLAB: Execution order

execution order

What is the easiest way to control execution order of your code?

i have a function that creates an array of numbers and then I have a for loop that needs to use some numbers from that array. but the for loop seesms to be executing first.

Best Answer

Matlab executes the code line by line in serial order. Inside a line the commands are executed from left to right.

Callbacks and timer functions are processed, if the command prompt is reached, or if PAUSE or DRAWNOW trigger their execution.

I do not see any possibilities to influence the order of execution.

Related Solutions

MATLAB: How to pause the execution of one timer while continuing to execute another timer in MATLAB 7.8 (R2009a)

The PAUSE statement in the timer's callback function will pause MATLAB execution completely. PAUSE will not stop the MATLAB execution if the PAUSE is outside the timer's TimerFcn callback.

To pause timer's execution,you can use timer's 'StartDelay' property. You can stop the timer at a certain point, set 'StartDelay' property of a timer, and then start the timer again. The timer's execution will start after 'StartDelay' amount of time elapses. Consider the following example:

function timer_test
t1 = timer('ExecutionMode','fixedRate','TimerFcn','disp(''Timer ONE is executing'')');
t2 = timer('ExecutionMode','fixedRate','TimerFcn','disp(''Timer TWO is executing'')');
% start both timers
start(t1)
start(t2)
% the timers continue executing despite the PAUSE statement
pause(3)
%stop the 1st timer
stop(t1)
disp('Timer 1 is stopped. Its execution will start in 3 seconds')
% set the timer's StartDelay property to introduce the pause in timer's execution
set(t1,'StartDelay',3)
%start the timer, it will start executing after 3 seconds have elapsed.
start(t1)
% continue running timers for 5 more seconds then stop the timers and delete them
pause(5)
stop(t1)
stop(t2)
delete(t1)
delete(t2)

MATLAB: Matlab timer is not executed asynchronously

The details are more complicated than Jan indicates. Multiple threads are used in some cases.

https://www.mathworks.com/matlabcentral/answers/21537-what-thread-do-timers-operate-in

https://www.mathworks.com/matlabcentral/answers/94884-is-there-variable-access-synchronization-between-matlab-main-execution-thread-and-spawned-java-threa

"For example, a timer object is in a different thread than the MATLAB main thread. But it cannot interrupt a single MATLAB command i.e. a variable copy command.

A block of MATLAB code can be interrupted by a timer object. Thus if a block of code operates on a variable, there is a possibility of data corruption.

However, Just-in-Time compilation (JIT) can execute several lines of code all at once in certain circumstances, in which case the timer will not be able to interrupt execution. If the interruption must happen in a particular place, a DRAWNOW command will ensure that one can occur. Otherwise, the DRAWNOW is not needed."

In your example possibly everything in your "for" loop got compiled into a single JIT block.

We are positive that internal calls to BLAS or LINPAK cannot be interrupted by timers. We believe (but are not certain) that no one source line of MATLAB code can be interrupted by timers. We are rather less certain about when multiple-line blocks can be interrupted by timers.

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Related Solutions

MATLAB: How to pause the execution of one timer while continuing to execute another timer in MATLAB 7.8 (R2009a)

MATLAB: Matlab timer is not executed asynchronously

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