Process oriented style DAG building in nested workflow

[gaow]

Separated from a discussion elsewhere, related to DAG: if i do have defined input and output for,

[method_1]
input: ...
output: ...

[method_2]
input: ...
output: ...

[another_method_1]
input: ...
output: ...

[another_method_2]
input: ...
output: ...

[default]
sos_run('method')
sos_run('another_method')

then in default the two sos_run will work in parallel, right? This is in fact exactly our process oriented example. I seem to recall at some point we have a no_wait option to sos_run to do this manually -- that's in case of input and output are not defined? In this case parallelization should be automatic?

and from @BoPeng

I played around with the idea for a while and found it doable, but still more complicated than I thought. Basically, anything touching the core mesh of messaging can cause unexpected outcome. I would keep this ticket open and see if I can get a chance to revisit.

[BoPeng]

No. The two sos_run are executed sequentially as a Python block. It is possible to add an option to it, something like

[default]
sos_run('method', concurrent=True)
sos_run('another_method', concurrent=True)

but I could not make it to work correctly given the possibilities that nested workflows can have nested workflows, tasks etc. As I said, it could work but it is not a priority for me now.

[gaow]

Resolved in #1167 with restrictions.