Warning: Could not launch SMPD process manager. Using fallback parallel mechanism.

The script is as follows:

 Lambdass = [0.0001, 0.001, 0.01, 0.1, 1, 10, 100, 1000];
 numcores = feature('numcores'); % get the number of cpu cores
 num_slices = floor(length(Lambdass)/numcores); % get the number of slices for parallel computing
 if mod(length(Lambdass), numcores)~=0
     num_slices = num_slices + 1;
 end
 for slice_i=1:num_slices
     if slice_i~=num_slices
         Lambdas = Lambdass(((slice_i-1)*numcores+1):((slice_i)*numcores));
     else
         Lambdas = Lambdass(((slice_i-1)*numcores+1):end);
     end 
     myparpool = parpool(length(Lambdas))
     parfor li = 1:length(Lambdas)
     %spmd
         lambda = Lambdas(li);
         save_path1 = sprintf('results/lambda_%f/', lambda);
         if ~exist([save_path1, '/fs_results.mat'], 'file') 
             do_something_and_save_results(lambda, save_path1);
         end
     end
     delete(myparpool)
 end

This script could be run correctly in one computer, but in another computer, the `parfor` seems to not work correctly and there are some warning information as follows, and the `parfor` finally runs without parallel mode, just seems the `for` in sequential. Could anyone help give some advice, please?

Starting parallel pool (parpool) using the 'local' profile ... Warning: Could not launch SMPD process manager. Using fallback parallel mechanism. 
> In SmpdGateway>SmpdGateway.canUseSmpd at 81
In Local.hSubmitCommunicatingJob at 15
In CJSCommunicatingJob>CJSCommunicatingJob.submitOneJob at 81
In Job.Job>Job.submit at 302
In InteractiveClient>InteractiveClient.start at 327
In Pool.Pool>iStartClient at 537
In Pool.Pool>Pool.hBuildPool at 434
In parpool at 104

[Edric Ellis]

That warning shouldn't prevent the pool from opening - and if you don't get an error from the parpool command, then the pool should have opened. How many cores does the machine have (as reported by " feature numcores ")? What OS is it running?

[None]

Hi, Edric, the results of "feature('numcores')" is:

>> feature('numcores')
MATLAB detected: 4 physical cores.
MATLAB detected: 8 logical cores.
MATLAB was assigned: 8 logical cores by the OS.
MATLAB is using: 4 logical cores.
MATLAB is not using all logical cores because hyper-threading is enabled.

ans =

       4

And the OS is Ubuntu 12.04 (64 bit).

I've tried the same script in another computer whose OS is also Ubuntu 12.04 (64 bit), but with just 2 cores (Intel E7400 processor). The script could run in parallel.

But in this computer which has 4 cores (Intel i7 processor), the script couldn't run in parallel, but in sequential. I'm not sure if some configuration may have an effect with it. But I always config the two computers with the same software environment in spite of the different hardware configuration.

And the parallel validation results are as follows:

VALIDATION DETAILS
Profile: local
Scheduler Type: Local

Stage: Cluster connection test (parcluster)
Status: Passed
Description:Validation Passed
Command Line Output:(none)
Error Report:(none)
Debug Log:(none)

Stage: Job test (createJob)
Status: Passed
Description:Validation Passed
Command Line Output:(none)
Error Report:(none)
Debug Log:(none)

Stage: SPMD job test (createCommunicatingJob)
Status: Passed
Description:Validation Passed
Command Line Output:
[Warning: Could not launch SMPD process manager. Using fallback parallel mechanism.] 
[> In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+apishared/SmpdGateway.m',81,1)">SmpdGateway>SmpdGateway.canUseSmpd at 81</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+cluster/@Local/hSubmitCommunicatingJob.m',15,1)">Local.hSubmitCommunicatingJob at 15</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+job/CJSCommunicatingJob.m',81,1)">CJSCommunicatingJob>CJSCommunicatingJob.submitOneJob at 81</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/@Job/Job.m',302,1)">Job.Job>Job.submit at 302</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',529,1)">Validator>iCreateAndSubmitJob at 529</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',258,1)">Validator>Validator.runJobStage at 258</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',207,1)">Validator>Validator.runValidationStages at 207</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',104,1)">Validator>Validator.validate at 104</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+ui/ValidationManager.m',45,1)">ValidationManager>ValidationManager.validate at 45</a>] 

Error Report:(none)
Debug Log:(none)

Stage: Pool job test (createCommunicatingJob)
Status: Passed
Description:Validation Passed
Command Line Output:
[Warning: Could not launch SMPD process manager. Using fallback parallel mechanism.] 
[> In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+apishared/SmpdGateway.m',81,1)">SmpdGateway>SmpdGateway.canUseSmpd at 81</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+cluster/@Local/hSubmitCommunicatingJob.m',15,1)">Local.hSubmitCommunicatingJob at 15</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+job/CJSCommunicatingJob.m',81,1)">CJSCommunicatingJob>CJSCommunicatingJob.submitOneJob at 81</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/@Job/Job.m',302,1)">Job.Job>Job.submit at 302</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',529,1)">Validator>iCreateAndSubmitJob at 529</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',258,1)">Validator>Validator.runJobStage at 258</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',207,1)">Validator>Validator.runValidationStages at 207</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',104,1)">Validator>Validator.validate at 104</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+ui/ValidationManager.m',45,1)">ValidationManager>ValidationManager.validate at 45</a>] 

Error Report:(none)
Debug Log:(none)

Stage: Parallel pool test (parpool)
Status: Passed
Description:Validation Passed
Command Line Output:
[Warning: Could not launch SMPD process manager. Using fallback parallel mechanism.] 
[> In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+apishared/SmpdGateway.m',81,1)">SmpdGateway>SmpdGateway.canUseSmpd at 81</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+cluster/@Local/hSubmitCommunicatingJob.m',15,1)">Local.hSubmitCommunicatingJob at 15</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+job/CJSCommunicatingJob.m',81,1)">CJSCommunicatingJob>CJSCommunicatingJob.submitOneJob at 81</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/@Job/Job.m',302,1)">Job.Job>Job.submit at 302</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+pool/InteractiveClient.m',327,1)">InteractiveClient>InteractiveClient.start at 327</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/@Pool/Pool.m',537,1)">Pool.Pool>iStartClient at 537</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/@Pool/Pool.m',434,1)">Pool.Pool>Pool.hBuildPool at 434</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',639,1)">Validator>iOpenPoolForCluster at 639</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',326,1)">Validator>@()iOpenPoolForCluster(cluster) at 326</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',328,1)">Validator>Validator.runInteractivePool at 328</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',219,1)">Validator>Validator.runValidationStages at 219</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+validator/Validator.m',104,1)">Validator>Validator.validate at 104</a>
  In <a href="matlab: opentoline('/usr/local/MATLAB/R2014b/toolbox/distcomp/cluster/+parallel/+internal/+ui/ValidationManager.m',45,1)">ValidationManager>ValidationManager.validate at 45</a>] 
connected to 4 workers.
Parallel pool using the 'local' profile is shutting down.
hAwaitWorkerCompletion on job 4 completed with result 1 in 2.851000e-03 seconds.

Error Report:(none)
Debug Log:(none)

[Meng-Yuan Huang]

I solved this problem: "Warning: Could not launch SMPD process manager. Using fallback parallel mechanism."

I found a file named ".smpd" in my home directory. Its file mode is 700. I changed it to 600 by chmod or deleted it, restarted MATLAB, and the SMPD problem was solved. I don't know what happen. (My MATLAB version is R2015b.)