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Optimisation of VASP Density Functional Theory (DFT)/Hartree-Fock (HF) hybrid functional code using mixed-mode parallelism

The VASP code is used for performing ab initio quantum mechanical total energy calculations and molecular dynamics (MD) simulations with pseudopotentials and a plane wave basis set. VASP employs a finite-temperature local-density approximation and an exact evaluation of the instantaneous electronic ground state at each MD-step. VASP is one of the most widely used applications on HECToR.

The key aims of the project are to:

  • Produce an efficient mixed-mode version of VASP.
  • Improve efficiency of the code by enabling more numbers of cores to be used on a cores per node basis.
  • Validate the mixed-mode version against a set of representative test cases.

The individual achievements of the project are summarised below:

  • Two new mixed-mode versions of VASP were developed by introducing OpenMP to the F90+MPI code.
  • The first version employs OpenMP directives within an extant VASP 5.2.12 routine, the result is 50% parallel efficiency, when comparing two and no OpenMP threads per MPI task. This will permit new science as users of this version can now double the number of cores used, thereby increasing the memory available.
  • The second version involves a complete restructuring of the DFT/HF code, and is inspired by a GPU-based version of VASP. Due to the scale of this task, the work is still in progress.
  • Furthermore, replacing the internal FFT routines with calls to the FFTW3 library was found to be beneficial. The version of the VASP centrally available to VASP users now employs the FFTW3 library.

Please see PDF or HTML for a report which summarises this project.