How to use parfeval?

can anyone will explain the syntax of F = parfeval(p,fcn,numout,in1,in2,...) this? p(builds parallel pool),fcn(is the function),What is numout,in1,in2? I have 3output from the function how can i use that output using fetchoutputs(f)? Kindly give answers.

Answer 1

[Walter Roberson]

You need to have an existing parpool stored in a variable that you pass in as the first parameter.

fun is the handle of the function to be executed.

If you need the third output then numout should be at least 3: the value should be the maximum number of output that you need from each call.

When you collect the output then you will get a cell array if I recall correctly, which you can index at {3}

[DhanaLakshmiR]

I don't know that i have used the syntax correctly. Help me with correct syntax.

function [xposition yposition altitude]=sixdof(xpos,ypos,alt)
xpos=xpos+velx*delt;
ypos=ypos+vely*delt;
alt=alt-velz*delt;
end

Im having the above code in separate mfile. I need this value simultaneously in another mfile so i have included parfeval. But i dont know about that concept.

p = gcp();
value=0;
while(1)
    Moving(value);
Default syntax is f=parfeval(p,@func,numout,in1,in2..)
so that i have used like this f = parfeval(p, @sixdof,3,1,2,3)     
    value = fetchOutputs(f)
end

In sixdof function i have 3outputs by using the above code can i get that value from sixdof function?

function[position values]= Moving(value)
 {
  body
  }

I want to fetch the output from the first mfile and have to be used in the above code can i? Kindly explain.

[Walter Roberson]

Yes, that should work.

However, remember that there is overhead is communicating with a parallel pool and asking it to do work and getting the results back, so using parfeval is slower if the work to be done is not "big enough" or if you do not have at least two workers processing data. In the code outline you show, you are always immediately waiting for the future you just created, so you will only ever have one future executing at a time, and the amount of work you are asking the future to do is trivial so the cost of using the parfeval will overwhelm any benefits. In the code you outline, you would be better off just calling sixdof directly without any parallel pool.

[DhanaLakshmiR]

Thank you for your explanation.