Ipopt 3.14 / spral

[PierreMartinon]

More recent ipopt builds enable the use of SPRAL instead of MUMPS via the option linear_solver = spral. Version 3.14+ of ipopt can be forced in the conda env .yaml file.

• linux: after some fiddling with the conda env (need to prune older gfortran version apparently), the spral option seems to work (need to set environment variable OMP_CANCELLATION=TRUE), although not obviously faster. Proper benchmark needed.
• macos: forcing ipopt 3.14 fails for now. To investigate.
• windows: broken anyway at the moment

[jbcaillau]

@PierreMartinon and Julia >= 1.9 needed if I am not mistaken.

[PierreMartinon]

Yes, but I had already switched to 1.9 a while ago. I'll have to check what the other env variable does (the BIND PROC something one): it seems you can use spral without it, but maybe this reduces performance. The spral testing will have to wait a bit anyway, I still need to get the 3.14 working on macos ... and repair/update the windows build.