How to run multiple functions simultaneously and communicate with each other?

Hello everyone. Here is my question:

Let's say I have 2 functions to run together with different but equal sized data. I want to call and run these functions simultaneously and in the future these functions are going to communicate with each other. So, based on my research I should work with spmd command. I have examined so many examples but I feel like I haven't figure out the command properly.

function a = aData()

a = 0;

for i = 1:100 a end

function b = bData()

b = 1;

for j = 1:100 b end

% To call them

parpool(2);

spmd

aData();

bData();

end

delete(gcp); % to avoid any error message

When I do this in the first place, I was expecting an output like : a b a b a b a b a b a b a b .. for 100 times.

Instead of that, I get a a a a a a a ... for 100 times and then b b b b b b b b... for 100 times.

Then I add a timer to hold aData for 10 seconds and check if bData is being called ahead for 10 seconds.

function a = aData()

a = 0;

T = timer('TimerFcn', @(~,~)disp('Fired.'), 'StartDelay', 10);

start(T)

wait(T)

for i = 1:100 a end

Didn't do any changes in bData function.

So I was expecting an output like : b b b b b b (for 10 s) a b a b a b a b a b a b .. a a a a a a (totaly 100 times each). But when I try the hold aData for 10 seconds, bData is also hold.

Here is what I get:

(No disp for 10 s)

After 10 s : b b b b b b // a a a a a a a (for 100 times) then b b b b b b b (for totally 100 times).

What am I doing wrong guys? Thanks in advance.

Answer 1

[Edric Ellis]

Your spmd block as written instructs each worker to run first aData() and then bData(). This is the general pattern of spmd - all workers execute the body simultaneously. If instead you want one worker to run aData() and the 2nd to run bData(), you should switch on the value of spmdIndex inside the spmd block, like this:

spmd
    if spmdIndex == 1
        aData();
    elseif spmdIndex == 2
        bData();
    end
end