Improved treatment of exact exchange in Quantum ESPRESSO
Here, we present an algorithm and implementation for the parallel computation of exact exchange in Quantum ESPRESSO (QE) that exhibits greatly improved strong scaling. QE is an opensource software package for electronic structure calculations using plane wave density functional theory, and supports the use of local, semilocal, and hybrid DFT functionals. Wider application of hybrid functionals is desirable for the improved simulation of electronic band energy alignments and thermodynamic properties, but the computational complexity of evaluating the exact exchange potential limits the practical application of hybrid functionals to large systems and requires efficient implementations. We demonstrate that existing implementations of hybrid DFT that utilize a single data structure for both the local and exact exchange regions of the code are significantly limited in the degree of parallelization achievable. We present a bandpair parallelization approach, in which the calculation of exact exchange is parallelized and evaluated independently from the parallelization of the remainder of the calculation, with the wavefunction data being efficiently transformed onthefly into a form that is optimal for each part of the calculation. For a 64 water molecule supercell, our new algorithm reduces the overall time to solution by nearly an order of magnitude.
 Authors:

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 Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
 Cray Inc., Saint Paul, MN (United States)
 Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
 Publication Date:
 Grant/Contract Number:
 AC0500OR22725; AC0205CH11231
 Type:
 Accepted Manuscript
 Journal Name:
 Computer Physics Communications
 Additional Journal Information:
 Journal Volume: 214; Journal Issue: C; Journal ID: ISSN 00104655
 Publisher:
 Elsevier
 Research Org:
 Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lawrence Berkeley National Lab. (LBNL), Berkeley, CA (United States)
 Sponsoring Org:
 USDOE Office of Science (SC), Advanced Scientific Computing Research (ASCR) (SC21)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 97 MATHEMATICS AND COMPUTING; Hybrid DFT; Quantum ESPRESSO; Scalability
 OSTI Identifier:
 1376349
 Alternate Identifier(s):
 OSTI ID: 1379829; OSTI ID: 1396579
Barnes, Taylor A., Kurth, Thorsten, Carrier, Pierre, Wichmann, Nathan, Prendergast, David, Kent, Paul R. C., and Deslippe, Jack. Improved treatment of exact exchange in Quantum ESPRESSO. United States: N. p.,
Web. doi:10.1016/j.cpc.2017.01.008.
Barnes, Taylor A., Kurth, Thorsten, Carrier, Pierre, Wichmann, Nathan, Prendergast, David, Kent, Paul R. C., & Deslippe, Jack. Improved treatment of exact exchange in Quantum ESPRESSO. United States. doi:10.1016/j.cpc.2017.01.008.
Barnes, Taylor A., Kurth, Thorsten, Carrier, Pierre, Wichmann, Nathan, Prendergast, David, Kent, Paul R. C., and Deslippe, Jack. 2017.
"Improved treatment of exact exchange in Quantum ESPRESSO". United States.
doi:10.1016/j.cpc.2017.01.008. https://www.osti.gov/servlets/purl/1376349.
@article{osti_1376349,
title = {Improved treatment of exact exchange in Quantum ESPRESSO},
author = {Barnes, Taylor A. and Kurth, Thorsten and Carrier, Pierre and Wichmann, Nathan and Prendergast, David and Kent, Paul R. C. and Deslippe, Jack},
abstractNote = {Here, we present an algorithm and implementation for the parallel computation of exact exchange in Quantum ESPRESSO (QE) that exhibits greatly improved strong scaling. QE is an opensource software package for electronic structure calculations using plane wave density functional theory, and supports the use of local, semilocal, and hybrid DFT functionals. Wider application of hybrid functionals is desirable for the improved simulation of electronic band energy alignments and thermodynamic properties, but the computational complexity of evaluating the exact exchange potential limits the practical application of hybrid functionals to large systems and requires efficient implementations. We demonstrate that existing implementations of hybrid DFT that utilize a single data structure for both the local and exact exchange regions of the code are significantly limited in the degree of parallelization achievable. We present a bandpair parallelization approach, in which the calculation of exact exchange is parallelized and evaluated independently from the parallelization of the remainder of the calculation, with the wavefunction data being efficiently transformed onthefly into a form that is optimal for each part of the calculation. For a 64 water molecule supercell, our new algorithm reduces the overall time to solution by nearly an order of magnitude.},
doi = {10.1016/j.cpc.2017.01.008},
journal = {Computer Physics Communications},
number = C,
volume = 214,
place = {United States},
year = {2017},
month = {1}
}