install prefix and library naming conventions

[torehl]

Hi QuEST developers,

would it be possible to include a CMAKE_INSTALL_PREFIX section in the CMakeLists.txt file?

In addition, I suggest you use a similar convention often used on HPC systems for the various threaded (mt/omp/gmp), distributed (mpi), and accelerated (GPU accelerated) versions of the library:

E.g. in $CMAKE_INSTALL_PREFIX/lib please rename the builds something like

libQuEST.so -> libQuEST.so.3.5.0
libQuEST.so.3.5.0
libQuEST-mt.so.3.5.0 -> libQuEST.so.3.5.0
libQuEST-mt+mpi.so.3.5.0
libQuEST-cu118.so.3.5.0

I ended up creating separate modules files that point to separate directories. Works as well, but probably the cleanest install.

24 /cm/shared/ex3-qc-modules/apps/QuEST/3.5.0/lib/omp
368 /cm/shared/ex3-qc-modules/apps/QuEST/3.5.0/lib/omp+mpi
1668 /cm/shared/ex3-qc-modules/apps/QuEST/3.5.0/lib/omp+cu118
2376 /cm/shared/ex3-qc-modules/apps/QuEST/3.5.0/lib
19968 /cm/shared/ex3-qc-modules/apps/QuEST/3.5.0/docs
64 /cm/shared/ex3-qc-modules/apps/QuEST/3.5.0/examples
628 /cm/shared/ex3-qc-modules/apps/QuEST/3.5.0/tests/catch
1176 /cm/shared/ex3-qc-modules/apps/QuEST/3.5.0/tests
304 /cm/shared/ex3-qc-modules/apps/QuEST/3.5.0/include
23904 /cm/shared/ex3-qc-modules/apps/QuEST/3.5.0/

A penny for your thoughts?

Ref:
https://cmake.org/cmake/help/latest/variable/CMAKE_INSTALL_PREFIX.html

[TysonRayJones]

Hi there,

Apologies for the profane delay! We currently do not intend users to make install QuEST because they are expected to recompile the entirety of QuEST (which takes mere seconds) when changing the deployment backend (e.g. from CPU to GPU).

You raise an interesting idea - that all backends could be separately compiled and installed to distinct directories. Each would still be installed separately so that a user needn't (e.g.) have CUDA installed just to compile QuEST for distributed simulation.

Still, to ensure a user runs the right deployment mode in HPC settings, we encourage re-compiling in that mode during job submission. It adds a few seconds to the job while significantly reducing the chance of wasting HPC resources by (e.g.) unknowingly running slow, serial CPU QuEST on a GPU node.

It may still be that adding CMAKE_INSTALL_PREFIX to the makefile enables more convenient optional installation. Unfortunately I've no experience with it - please feel free to make a pull request with the proposed change!