Why is compiled parfor repeatedly trying to start a parallel pool?

Situation: MATLAB 2015b, CentOS Linux 7, Compiler & Parallel toolboxes installed on machine, Parallel not licensed. Uncompiled: code works fine (parfor loops work like for loops in reverse since the Parallel Toolbox is not licensed). Compiled: at each parfor loop, code tries to start parallel pool (wasting >10 sec).

Example code:

    function out = TestPar(s1,s2)
      s1=str2num(s1);s2=str2num(s2);
      out=zeros(1,s1);
      for k = 1:3,
         parfor p=1:numel(out),
            out(p) = mean(mean(rand(s2,s2)));
         end
      end

Code Execution uncompiled: TestPar('10000','155') Code Execution compiled: system('TestPar 10000 155')

Answer 1

[OCDER]

Your compiled application (which is pre 2016a) has access to parallel processing and will use the default parallel setting, which is to autocreate a parpool when a parfor is encountered. Change the default setting for this autocreate feature before compiling, since the compiled application will use the default setting of your machine.

To fix:

ps = parallel.Settings;
ps.Pool.AutoCreate = false; %will prevent parpool from activating when encountering parfor

[Walter Roberson]

The behaviour changed as of R2016a; see https://www.mathworks.com/matlabcentral/answers/270249-does-matlab-compiler-checkout-toolbox-licenses-at-compile-time

[OCDER]

Thanks Walter for this info!

[Mark Manzardo]

I've validated a work around for my situation in part thanks to the fix Donald suggested (Thanks for pointing me in the right direction). The following was required to maintain functionality in uncompiled and compiled versions for both Windows and Linux environments given my situation:

if true
IsPar = true;
try
 if isempty(gcp('create'))
    ps = parallel.Settings;
    if ps.Pool.AutoCreate
       parpool(parcluster);
    end
 end
catch
 IsPar = false;
 try
    ps.Pool.AutoCreate = false;
 catch
 end
end
end

The IsPar flag is used later throughout the code to prevent failure conditions when other PCT functions (i.e., other than parfor) are encountered in the code. NOTE: this was all necessary because license('test','Distrib_Computing_Toolbox') doesn't work like it should specifically for my situation on Linux when compiled.