Fix Incorrect Usage of Rank/Task/etc. in Environment Chapter

[wesbland]

Problem

Replace the incorrect usage of the words "rank", "task", etc. to be correctly specified and reflective of the underlying group, communicator, file, or window.

Proposal

Read through the entire chapter to find all problematic instances and correct them.

Changes to the Text

There is unlikely to be a one-size-fits-all solution so the chapter committee will need to consider each occurrence.

Impact on Implementations

None

Impact on Users

We will hopefully begin the process of avoiding the incorrect terminology of referring to processes as ranks and other incorrect usages.

References and Pull Requests

There was a catch-all issue to correct this in #455, but this is being divided up to cover all chapters.

This chapter is covered by https://github.com/mpi-forum/mpi-standard/pull/669.

[bosilca]

Nothing to be done in the environment chapter (with the exception of getting the historic 486 implemented).

[wesbland]

IMO, there are a couple of places that could use some clarification here:

• (p. 453, line 11, MPI 4.0) - MPI_HOST Host process rank, if such exists, MPI_PROC_NULL, otherwise.
• (p. 453, lines 13-14, MPI 4.0) - MPI_IO rank of a node that has regular I/O facilities (possibly myrank). Nodes in the same communicator may return different values for this parameter.
  • The above two items could be clarified by saying something like "as defined below" to reference the full text later.
• (p. 454, lines 2-3, MPI 4.0) - The value returned for MPI_IO is the rank of a processor that can provide language-standard I/O facilities.
  • This could say something similar to the previous entry for "Host Rank":

The value returned for MPI_HOST gets the rank of the HOST process in the group associated with communicator MPI_COMM_WORLD, if there is such. MPI_PROC_NULL is returned if there is no host.

[wesbland]

I've made some changes in https://github.com/mpi-forum/mpi-standard/pull/669 to address the concerns above. @bosilca @raffenet @naughtont3, please have a look.