Clarification on PMIx_Spawn info attributes

[naughtont3]

Describe your question or clarification request here

The specification for PMIx_Spawn() and PMIx_Spawn_nb() include a list of attributes that can be passed via the info key/values. The below text indicates these pmix_info_t items may be passed via the job_info or app arguments.

Should this be clarified to indicate what info items are valid to be passed via the job_info or app arg (or both)?

Suggested Clarification

In practice, when using PRRTE-2.0.2 and OpenPMIx-4.1.2, we found that some attributes (e.g., PMIX_MAPBY) needed to be in the job_info area of spawn. It is unclear if this is purely an implementation detail or something that should be clarified in the specification.

Based on this determination, we will either draft suggested text for the body or at least an advise to user remark.

References

Please list specific chapters/sections in the PMIx Standard related to your query.

Text from PMIx-4.0 spec under PMIx_Spawn (Page 159, Lines 32-33)

... In addition, they are required to support the following attributes when present in 
either the job_info or the info array of an element of the apps array:

[rhc54]

In practice, when using PRRTE-2.0.2 and OpenPMIx-4.1.2, we found that some attributes (e.g., PMIX_MAPBY) needed to be in the job_info area of spawn. It is unclear if this is purely an implementation detail or something that should be clarified in the specification.

I noticed the map-by constraint myself the other day. Currently, PRRTE doesn't support different mapping strategies per app in the same job. It would be a pretty significant effort to change that, and I'm not sure if it would be worth the effort.

Do you have a use-case that requires different mapping strategies for apps in the same job?

[naughtont3]

No, we don't have a use case. It was more a matter of a snafu when using it and not knowing exactly where to put the info key. I agree it might be kind of difficult to do per-app mapping strategies. I was thinking we might want to clarify, maybe as an advise to user, that currently the following XYZ attributes are only supported at the overall job level.

[rhc54]

Yeah, probably should just clarify better what goes into each of the two arrays, and what can go into either/both of them.

[naughtont3]

OK, i'll try to take a swing at that text. Main question will be formatting and identifying what attrs below in which array or both.

[jjhursey]

@naughtont3 have you had a chance to make a pass at some text here, or do you need help?

[naughtont3]

I took a quick look last week. I think the main issue is that it is unclear how we want to annotate items that should be in (J)ob or (A)pp, or both. I do not think we want to add another listing, so maybe add a flag or marker next to the attribute (e.g., (J), (A), (J,A) to indicate only Job, only App arrary or appear in both/either, respectively.