Codecov Report

Merging #1162 (3ed06d3) into main (698c51c) will decrease coverage by 0.00%.
The diff coverage is 38.88%.

@@            Coverage Diff             @@
##             main    #1162      +/-   ##
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- Coverage   65.10%   65.10%   -0.01%     
==========================================
  Files         315      315              
  Lines       45258    45264       +6     
  Branches    19240    19244       +4     
==========================================
+ Hits        29467    29469       +2     
- Misses      13329    13331       +2     
- Partials     2462     2464       +2     

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@ischoegl

One question that arises here is that with the inclusion of 6.0, there are 5 major Sundials version supported, with the last release of 2.7 being more than 5 years old (and version 2.4 dating back to 2009). Some of the preprocessor branches could be simplified if a minimum version of CT_SUNDIALS_VERSION >= 30 would be required.

I've wondered the same thing... I've always held back because I'm not sure what versions various HPC services might be using. 10 years is not a super long time for them... Certainly, the pace of SUNDIALS development has picked up in the last few years, so this is becoming a bigger concern though.

@bryanwweber ... yes, I am aware of HPC and generally agree. At the same time, Cantera is a somewhat odd application for HPC (unless it is tied into user code), as there really isn't much of an advantage to put things on a cluster based on how Sundials is being used at the moment?

I did consider dropping support for some older Sundials versions as part of this. However, Ubuntu 18.04 has Sundials 2.7, and I'd like to continue supporting that fully at least until it enters the "extended maintenance" period in Fall 2022. So I think we can drop support for Sundials 2.x after the Cantera 2.6 release.

Looking further ahead, Ubuntu 20.04 has Sundials 3.1, so I guess I would expect to continue supporting that through Fall 2024.

Checking pkgs.org, CentOS 7 is also on Sundials 2.7, is set to receive maintenance updates until 2024-06-30 (https://wiki.centos.org/About/Product), and is what's presently being used by the HPCs that I use.
Good news is that once the jump is made from EL7 to EL8, sundials jumps to 5.8 (although with the CentOS situation, who knows when and to what exact distro those EL7 clusters will upgrade)

I think the next version of Cantera after 2.6 will be 3.0, so with the major version bump, I think dropping support for Sundials 2.7 would make sense. That will likely occur sometime in 2023 given recent release cadence, so it'd be a much smaller remaining support window for CentOS 7 than it looks right now 😄