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Advice on paralllel builds

Posted: 06 Feb 2020, 17:20
by mikep219
[Standard caveat: I'm an HPC Sysadmin, not a Chemist]

One of our local Chemists has asked me to build and install Dalton on our cluster. I'm using Intel compilers with the following build options:

./setup --mpi --mkl=sequential

and some of the ctest checks are failing with the error:

WARNING: CC is not MPI parallelized!
For parallelization speedup, e.g. use parallel MKL

ERROR: CC not implemented for parallel calculations

If I'm reading that correctly, that's an expected error for this build type? Is there a minimum set of different parallel build types that ensure each type
of model being run gets the most out of parallelism? (I'm seeing MPI, OpenMP and MKL parallelism as options, and I'm wary that trying to build all three into a single binary might not be best approach)

Re: Advice on paralllel builds

Posted: 07 Feb 2020, 00:50
by taylor
As far as I know there is no OpenMP parallelism in Dalton, so that possibility is not relevant. Quite a lot of the code for calculating molecular properties is MPI parallelized and exploiting that will give a speed-up for some calculations. However, there is, as the output indicates, no MPI functionality in the coupled-cluster (CC) part of the code. On the other hand, the program makes considerable use of matrix operations, so use of the threaded MKL can give performance benefits. This applies to the CC part as well as the other parts of the code.

Best regards
P.S. Sorry, I cannot help with your phosphorescence question.

Re: Advice on paralllel builds

Posted: 07 Feb 2020, 15:53
by mikep219
Thanks for the advice. Looking at the help output for the setup script, I'm seeing an option "--omp" for OpenMP - I'm also seeing several omp pragma lines in the C++ source code files. Maybe this is a new feature for Dalton?

Re: Advice on paralllel builds

Posted: 07 Feb 2020, 16:02
by magnus
It is mostly a leftover from a few years back when the Dalton and LSDalton (which supports OpenMP) codes shared the same repository and setup files. These will be cleaned for the upcoming release. Also the omp pragmas that you see are in parts of the code that are not in use and will likely be removed soon.

Re: Advice on paralllel builds

Posted: 07 Feb 2020, 16:18
by mikep219
Thanks for explaining - that cuts down the number of test builds I need to try!