How to retrieve Toggle Button value during SPMD

Hi everyone,

i've a problem, i want launch two parallel while-cycles with SPMD, however i want stop them not when they finish but when the Toggle Button value is 1. If the SPMD isn't the right way, there's another way to execute parallel function and stop them with Toggle Button?

Thanks, Niccolò

Answer 1

[Walter Roberson]

spmd sessions cannot interact with graphics, and there is no non-spmd thread that is in control that could handle the graphics.

You might be able to use parfeval() instead; see https://www.mathworks.com/matlabcentral/answers/114033-waitbar-in-a-spmd-block-in-a-gui

Answer 2

[Roman Müller-Hainbach]

A workaround for sharing information across multiple threads of execution is using your file system. Write the toggle button status in a file on your hard drive. Then each SPMD branch can read that file.

[Niccolò de Cesare]

Ok this is a good idea! But after if i want write the output (for example on one worker i put a timer() function that every second give me the elapsed time) into a GUI textLabel can i do it?

Because i've developed an app that controls a servo-motor (servo-motor pulse with a set pause by user) and i would like to that at the same time another script called timer() calculate the elapsed time and write it on a label into the GUI every second; in fact pause of timer() is always the same but not the servo's pause, thus i thought that the parallel toolbox works fine for that but i don't know how interact with the GUI during SPMD.

[Walter Roberson]

When you are using SPMD, you cannot get at the current toggle button status. There is no lab that is defined as assigned to the original hardware, and there is no non-lab thread that is defined as being left running.

I have not tested graphics callbacks under the situation, but graphics callbacks are defined to happen only at boundaries of pause() or drawnow() or waitfor() or a figure being made active, and none of those can happen in the same thread when SPMD is running.

If there is any potential it would have to be through timer callbacks, as those are defined to be able to interrupt in some other circumstances as well.