how do i slice a variable in parfor?

Hi,

I am new to matlab, so I have this code here

function [ ] = test2()
h = EmotivEEG;
h.Run

parfor i = 1:5
    data_local = h.data;
    data_local = data_local+rand(1);
    plot(data_local)
    pause(0.5);
end
delete(h);
end

which h.run starts the function in EmotivEEG.m, delete(m) closes the connection to Emotiv.

I trued using parfor but i get "h variable is indexed but not sliced".

so data_local updates the plot every 0.5 seconds. What i wanted to do was to create a same loop and use its data some where else parallel.

I do have a parallel computing tool box could anyone tell me how to use parfor and matlabpool.

Answer 1

[Matt J]

What i wanted to do was to create a same loop and use its data some where else parallel.

And you want each parallel worker to use the entire data from h? If so, there's nothing wrong with the code as you've shown it.

The code analyzer warning is just telling you that this will result in h being copied and broadcast N times, where N is the number of workers. If the workers don't need all of the data from h, then there are ways to send only the pieces it needs, which reduces data copying and broadcast effort.

[akshay raj]

@mattthanks for the quick answer, sorry for the typo. will I be able to plot two figures at the same time without waiting for the first loop to finish? like

function [ ] = test2()
h = EmotivEEG;
h.Run
parfor ii = 1:5
    data_local = h.data;
    data_local = data_local+rand(1);
    plot(data_local)
    pause(0.5);
end

parfor k = 1:5
    data_local2 = h.data;
    data_local2 = data_local2;
    plot(data_local2)
    pause(0.5);
end
delete(h);
end

[Matt J]

No, successive parfor loops are executed sequentially. Also, you won't be able to generate plots inside a parfor loop. The parfor workers don't have displays. But you can do things like this:

parfor ii = 1:5

    data_local{i} = h.data + rand(1);

end

for i=1:5
  figure(i);
  plot(data_local{i})
end

[akshay raj]

Thanks @matt... could you please see my other question here getappdata-setappadata