Gnu Parallel : nested parallelism

Question

Is it possible to call gnu parallel from within multiple runs of a script that are in-turn spawned by gnu parallel?

I have a python script that runs for 100s of

Answer 1

Yes. GNU Parallel is designed (and tested heavily) to be able to be called from GNU Parallel - either directly or through a script.

If called directly you are likely to need to change -I. What does the second {} mean here (does it refer to the first or the second parallel?):

seq 10 | parallel 'seq {} | parallel echo {}'

Here it is very clear:

seq 10 | parallel 'seq {} | parallel -I // echo //'
seq 10 | parallel 'seq {} | parallel -I // echo {} //'

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