points example lacking point data

[pkestene]

Description

Currently the "points" examples are disabled in the cmake build.
These examples require pts data files (one file per MPI process).

There is also a comment in example/CMakelist.txt stating the points data files are missing, so that why the example is disabled in the cmake build (while still enabled in the autotools build) .

Proposed solution

• provide a simple executable that generate some point data to avoid distributing binary data files
• instead of generating one point data file per MPI process, just use MPI-IO to make reading / writing the point data file a MPI collective operation. One advantage is that user can easily generate data for any number of MPI processes, and read them with a possibly different number of MPI processes as easily.

[cburstedde]

Thanks for thinking this forward!

[cburstedde]

I'm merging #212, which resolves the issue. We may keep this issue open low-priority to play with the location of the generated points some more depending on the connectivity.

Likewise, adding the sc_io error handling will be instructive with this example.

[cburstedde]

While we do not distribute a points data file, we have a program to generate points on demand. Currently, the points are created randomly within a cube. This works well if the domain to generate is indeed the unit cube. For other connectivities/geometries, it would be desirable to query the bounding box of each tree and to generate points within their domains. Alternatively, we may add options to generate points according to an analytic distribution with a support wide enough that it covers all of our predefined geometries.