You can think subnames as attached strings to elements in a pvar. Whether a pvar has subnames or not is optional. So I proposed MPI_T_pvar_has_subnames() to query that. --Junchao Zhang On Thu, Nov 14, 2013 at 10:57 AM, Jeff Squyres (jsquyres) < [email protected]> wrote:

On Nov 13, 2013, at 6:13 PM, Junchao Zhang <[email protected]> wrote:

...

Let me comment on the problem in your slides of last teleconf: Slide 2: "Problem: multiple network devices on a server – want to return the number of sends on each device but don’t want to create a new variable for each of them. Solution: have each performance variable return an array of values; one for each underlying network device"

That basically says " (an MPI implementor) creates a multi-element pvar (i.e., pvar with count > 1)"

Slide 3: "Problem: But how do you know which array slot maps to which underlying Linux device? Solution: the btl_usnic_devices state performance variable."

I suppose "YOU" in the problem is an MPI_T user, for example, a tool developer. The question is distilled into "the user wants to know names of elements in a multi-element pvar".

We didn't talk about this on the call today.

I don't think I agree with your above statement. It's not the *name* of the pvar that is the issue -- a pvar already has a well-defined name. It's what each element of a pvar value *corresponds to*. In this case, we have a pvar with N elements in its value, and the implementation is corresponding each element to a Linux device (and it is desirable for the MPI_T user to know what that correspondence is).

We therefore want a way to express that relationship: that each element has a string corresponding to it (that is not necessarily a "name" or "subname"). However, not all pvars have this kind of relationship.

-- Jeff Squyres [email protected] For corporate legal information go to: http://www.cisco.com/web/about/doing_business/legal/cri/

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