I would like to install ifort 19.1 to use with MS visual studio 2019. The warning I get is that ifort 17 will be uninstalled if I proceed. It is critical to retain VS 2015 with ifort 17.1 for production use while I test VS 2019 and ifort 19.1 as a potential upgrade. Is there a way I can retain VS 2015/ifort 17.1 but install VS2019 with ifort 19.1?
Intel® Visual Fortran Compiler 17.0 Integration(s) in Microsoft Visual Studio* is already installed.
If you proceed to install, the Intel Visual Fortran Compiler 17.0 IDE integration(s) will be uninstalled and the Intel(R) Parallel Studio XE 2020 Cluster Edition for Windows* IDE integration will be installed. You will no longer be able to select 17.0 or older Intel Visual Fortran Compilers from the Visual Studio IDE (if it is currently installed).
Thanks, I have a short window where I have permission to install anything.
That's not what it says. Only one compiler's version of the Visual Studio integration can be present in a specific version of VS at a time. The new integration has some support for older compiler versions, but only those that supported the specific VS version. The 17 compiler never supported VS2019, so this doesn't matter.
For information on how to keep multiple VS versions going and use different compilers, see https://software.intel.com/en-us/articles/using-older-intel-visual-fortran-versions-in-different-microsoft-visual-studio-versions
It should not uninstall ifort 17 from VS2015, but if you are concerned with that, follow the instructions towards the bottom of the article I linked above.