[Eeglablist] Reproducible ICA

[ivano triggiani]

I have read more about the issue, and, apparently, when you use parfor,
every thread works independently with a different random seed.
I searched on the internet and I found that a solution could be something
like this:

s = RandStream.create('mrg32k3a', 'NumStreams', length(Files), 'Seed', 42);
%this should create a series of random seeds that you can control in the
loop.
parfor i = 1:length(Files)
    RandStream.setGlobalStream(s(i));
    run_preproc(Files{i});
end

I hope this helps.

Ivano

---

*Antonio Ivano Triggiani, Ph.D.*


________________________________________________



On Wed, Jul 2, 2025 at 12:16 PM Scott Makeig via eeglablist <
eeglablist at sccn.ucsd.edu> wrote:

> Christoph -
>
> There is an input parameter to runica() to set the random seed.   If this
> is not exposed in pop_runica(), you should be able to easily write a script
> to run runica() directly on your data. Else, there may be an option in
> pop_runica() to add optional runica() arguments...
>
> However, the differences in runica() output using different random seeds
> typically affect noticeably only the smallest (highest-index) ICs; they
> arise from variations in order of processing in successive runica  learning
> steps. As there is no canonical ('correct') order for (extended) infomax
> ICA to process the data, these variations define a (small) inherent
> ICA-noise data subspace....
>
> Scott Makeig
>
>
>
> On Mon, Jun 30, 2025 at 9:51 PM Frühlinger, Christoph via eeglablist <
> eeglablist at sccn.ucsd.edu> wrote:
>
> > Dear all,
> >
> > I want to insert a random seed in my preprocessing script before the ICA
> > to get reproducible results. I have tried several settings of the random
> > seed at different locations in the script (at the top, right before the
> > ICA, at the top of the pop_runica() function) as suggested in previous
> > threads of the mailing list. However, I keep getting different ICA
> results
> > for the same dataset. Some (potentially) relevant notes regarding the
> > script: I use a parfor loop to call the actual preprocessing function
> like:
> >
> > ```
> > parfor i_Sub = 1:length(Files)
> >                 run_preproc()
> > end
> >
> > function run_preproc()
> >                 # basic preprocessing
> >
> >                 EEG = pop_runica(EEG, 'icatype', 'runica', 'pca', rank,
> > 'extended', 1, 'interupt', 'off');
> >
> >                 # some more preprocessing
> > end
> > ```
> >
> > I would appreciate it if you could help me!
> >
> > Best wishes
> > Christoph
> > _______________________________________________
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> >
>
>
> --
> Scott Makeig, Research Scientist and Director, Swartz Center for
> Computational Neuroscience, Institute for Neural Computation, University of
> California San Diego, La Jolla CA 92093-0559, http://sccn.ucsd.edu/~scott 
> _______________________________________________
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