Do MATLAB GUI buttons create parallel strands if pressed multiple times?

So i have a GUI with a button to gather data from a USB device. when pressed the button triggers a sequential code to recover data from the device.

My question is, could multiple presses trigger multiple instances of the same code to run either deliberately or through the absence of a particular code to prevent it?

If so, and it affects the displayed figure, which process has priority?

Thanks,

Jason

Answer 1

[Walter Roberson]

You would need to have specific use of the Parallel Computing Toolbox such as parfor() or spmd() or parfeval() in order to have multiple parallel instances of the same code.

However in some cases it is possible for a callback to suspend a different callback. See the description of https://www.mathworks.com/help/matlab/ref/uicontrol-properties.html#zmw57dd0e1042342 the Interruptible and BusyAction properties.

Answer 2

[Jason Riley]

Walter,

Thanks for the rapid response. So as i understand it, the second click could cause a second version of the process to interupt the first version of the process - what happens to the first version, does it terminate, or does it sit in background and await control again?

as the two are both to-ing and fro-ing over the USB bus, could this cause speed issues?

Thanks again,

Jason

[Walter Roberson]

The first would be suspended.

Note that there are limited circumstances in which the interrupt can be be considered for service: pause(), waitfor(), uiwait(), figure(), drawnow(), keyboard(). If you do not have those in your code then MATLAB will just queue the event without any checks until it is allowed to look at the queue to process the Interruptible BusyAction test

[Walter Roberson]

It has never been really clear under what conditions a listener can fire, or a serial or instrument or daq callback can fire. Buried somewhere in the documentation is a note a couple of years ago that timers can be serviced every source line, which is an exception to the drawnow / pause rule.

[Jason Riley]

ah, I do have a repeated call to 'drawnow' to update the figure as we go along, so its obviously picking that up as the point to subvert control. i'll check the other commands, because i am using some manufacturer code on the DAQ box as well that could cause the issue. I think this is likely my problem. I will write code to disable the button once pressed until the program has completed. i had thought it was implicit from the linear code - my mistake.

[Walter Roberson]

Disabling the button is a good idea.