correctly determine INTEL_ROOT_DEFAULT using MKLROOT env variable

[alexlnkp]

As mentioned in the issue #1703 , MKLROOT env variable is set to /opt/intel/oneapi/mkl/latest, which makes sense. However, CMakeLists.txt tries to find the root of INTEL by going one dir up. set(INTEL_ROOT_DEFAULT $ENV{MKLROOT}/... This wouldn't work, as the MKLROOT points to the latest, not oneapi. Therefore, to fix this - it's better to go 3 directories up, so that if MKLROOT is /opt/intel/oneapi/mkl/latest, it would correctly point to the root of INTEL.

[minhthuc2502]

Hello, this change will break the compilation on Windows. For the environment like Arch, you can set variable environment like INTELROOT or MKLROOT to make it work as you did in the issue (this action is expected for certain OS). No PR is needed.

[alexlnkp]

Hello, this change will break the compilation on Windows. For the environment like Arch, you can set variable environment like INTELROOT or MKLROOT to make it work as you did in the issue (this action is expected for certain OS). No PR is needed.

I mean, i could add a check for the OS and then check the paths, not sure if this would help anyone but me though.
I made this PR for people like me, who used pacman and yay to install all of the stuff the CTranslate2 needs, so i believe that this idea is more or less valid for at least the arch users.
Please let me know if some of the suggestions i made are valid.

[minhthuc2502]

If you don't set anything, INTEL_ROOT_DEFAULT will be /opt/intel . Otherwise, in your case, MKLROOT env variable is set to /opt/intel/oneapi/mkl/latest, then you set set(INTEL_ROOT_DEFAULT $ENV{MKLROOT}/../../..), the INTEL_ROOT_DEFAULT would be /opt/intel. Something I missed here? Why you have to set MKLROOT?

[alexlnkp]

If you don't set anything, INTEL_ROOT_DEFAULT will be /opt/intel . Otherwise, in your case, MKLROOT env variable is set to /opt/intel/oneapi/mkl/latest, then you set set(INTEL_ROOT_DEFAULT $ENV{MKLROOT}/../../..), the INTEL_ROOT_DEFAULT would be /opt/intel. Something I missed here? Why you have to set MKLROOT?

That's the neat part! I didn't set MKLROOT. The package which is used to install the intel MKL stuff sets the env variable MKLROOT automatically via the INTEL's shell script, that was the main cause of the #1703 .
The shell script in question is /opt/intel/oneapi/mkl/latest/env/vars.sh

[minhthuc2502]

I see, You can do like this:

elseif(DEFINED ENV{MKLROOT})
  if(WIN32)
    set(INTEL_ROOT_DEFAULT $ENV{MKLROOT}/..)
  else()
   # Other system like arch set env MKLROOT by default
   set(INTEL_ROOT_DEFAULT $ENV{MKLROOT}/../../..) 

[alexlnkp]

I see, You can do like this:

elseif(DEFINED ENV{MKLROOT})
  if(WIN32)
    set(INTEL_ROOT_DEFAULT $ENV{MKLROOT}/..)
  else()
   # Other system like arch set env MKLROOT by default
   set(INTEL_ROOT_DEFAULT $ENV{MKLROOT}/../../..) 

Alrighty, i'll do that.
Though, do you want me to squash this change into previous commit so it's just a single-commit PR or should i just have 2 commits here?

[minhthuc2502]

Don't worry about squashing. I'll do when merge it.