Should new versions of hpc-stack be installed separately so they can co-exist with older versions?

[edwardhartnett]

@Hang-Lei-NOAA asks:

Should we do the separate installations, like Kyle did on wcoss2, is a question.

[edwardhartnett]

There is some discussion between @aerorahul and @climbfuji regarding this question: #303

In one sense, separate installs are unnecessary, since the existing hpc-stack grows to accommodate new versions. Therefore, there need be only one hpc-stack installation.

On the other hand, hpc-stack accomplishes a binning of the dependent libraries into a hpc-stack release. The 1.1.0 release of hpc-stack represents a number of libraries, with a specific range of versions. hpc-stack-1.2.0 represents an exact copy of those versions now, but over time, its versions will change and, by the time hpc-stack-1.3.0 is released, the 1.2.0 release will represent a different range of versions, with additional libraries added, and perhaps even some libraries removed.

HPC applications can be thought of as working with hpc-stack-1.1.0 or 1.2.0. Programmers can try to upgrade all their libraries to the latest version by