Automatically Assigning base workspace variables

I have almost 250 variables that I need to assign in the base workspace inside a PARFOR loop. Is there an automated way of doing this other than writing assignin('base','var',var) for each variables?

[Image Analyst]

Why do they need to go into the base workspace? That sounds crazy to me. Why don't you just return them from your function to the calling routine, or pass them via a mat file or setappdata() or something? I never send variables from a function's workspace into the base workspace - ever!

[Walter Roberson]

.mat file would be relatively slow for large data. setappdata() in theory relies upon graphics being available: it is not clear that the root graphics object exists on a node without graphics, such as would be the case for parfor. And then there is the fact that it is parfor. There was a case about 2 weeks ago in which variables had to be defined via assignin('base') in order to make them available to Simulink for the one simulation per worker case.

[Abhijit]

Well, I am trying to do parallel simulation and one of the matlab webinars say that variables have to be assigned for each simulink model's variable into the base workspace for parallel simulation.

As Walter had mentioned variables had to be defined via assignin in order to make them available.

[Image Analyst]

OK - I don't have Simulink. I added it to the product list for you so others will know.

Answer 1

[Walter Roberson]

Avoid doing that. For example create only a single struct and assignin() the struct.

http://matlab.wikia.com/wiki/FAQ#How_can_I_create_variables_A1.2C_A2.2C....2CA10_in_a_loop.3F

[Abhijit]

I am not sure if I follow: How would I replace the following 4 assignin commands for a, b , c and d variables as per your suggestion. This is a simple case.

In my case The variable gets generated depending upon the configuration I choose. Either way , I have bunch of variables that I need to assign inside PARFOR. Thanks a lot

a = -1; 
b = 1; 
c = 1; 
d = 0;
KIdx = 0:0.1:1;
iterations          = length(KIdx);
simout(iterations)  = Simulink.SimulationOutput;

parfor idx = 1:iterations
    load_system(mdl);
    assignin('base','K',KIdx(idx));
    assignin('base','a',a);
    assignin('base','b',b);
    assignin('base','c',c);
    assignin('base','d',d);
    try
        simout(idx) = sim(mdl,'SimulationMode','normal');
    catch exception
        error_var{idx} = lasterror
        stack_var{idx} = dbstack
        exception_var{idx} = getReport(exception,'extended')

      end

end

[Jan]

Assigning variables from inside a parfor loop is not useful. They are assign in each thread and would overwrite each other.

[Abhijit]

So , what are my options for assigning a,b,c,d values above? I thought you have to do assignin or evalin inside a parfor loop

To avoid overwriting should I create a temp directory and load the model and assign the variable in each directory?

[Walter Roberson]

Jan, The technique was approved by a Mathworks person a couple of weeks ago.

[Abhijit]

Hi Walter, Thanks for your answer. Structure would work for the simple exam I showed.

In my actual problem, the variables are getting generated behind the scenes. So, are there any other way for doing this? Can I leverage WHO in some way to do this.

[Abhijit]

I think I have figured out a way.

a = -1; 
b = 1; 
c = 1; 
d = 0;

W = who; 
for i1 = 1:length(W)
    Wval{i1} = eval(W{i1});
end
KIdx = 0:0.1:1;
iterations          = length(KIdx);
simout(iterations)  = Simulink.SimulationOutput;

parfor idx = 1:iterations

      load_system(mdl); 

      for i1 = 1:length(W)
          assignin('base',W{i1},Wval{i1});
      end
      assignin('base','K',KIdx(idx));

      try
          simout(idx) = sim(mdl,'SimulationMode','normal'); 

      catch exception
          error_var{idx} = lasterror
          stack_var{idx} = dbstack
          exception_var{idx} = getReport(exception,'extended')

      end

end

Answer 2

[David Arriola]

I have a similar problem to the one described above. I tried the solution proposed by Abhijit but I always get the following error: - Can somebody help me to get this right?

"It is illegal to use a Composite within the body of a parfor loop

Caused by: Error using distcomp.remoteparfor (line 72) Composite objects cannot be used within a parfor loop."

My code can be seen below:

 list = who;       
    N = length(list);

    for  j = 1:N
      w{j} = eval(list{j});
    end

    spmd
    % Setup tempdir and cd into it
    addpath(pwd);
    currDir = pwd;
    addpath(currDir);
    tmpDir = tempname;
    mkdir(tmpDir);
    cd(tmpDir);
    end

    %Set parameter values with reduced comb. matrix and simulate all combs.
    parfor m = 1:1:num_comb_red      
            load_system(uParam.sysInfo.modelName); % Load the model parameters on the workers       
            for  j = 1:N
                assignin('base',list{j}, w{j});
            end
        for n = 1:1:num_input_param
            num_value_red = cell2mat(comb_red(n,m));
            path = cell2mat(uParam.uncertainties.all{n,1});
            para_name = uParam.uncertainties.all{n,2};
            para_value = uParam.uncertainties.all{n,3}(num_value_red);
            set_param(path,para_name,num2str(para_value));
        end                        
        %Simulate model for all uncertainty combinations and all temperatures
        disp('Simulating linear model...')
        simOut(i,m) = sim(uParam.sysInfo.modelName,'SimulationMode', uParam.simInfo.simMode, 'StopTime', uParam.simInfo.simTime);
        disp('finished')  
    end