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Double Precision Is Not Needed for Many-Body Calculations: New Conventional Wisdom

preprint
submitted on 07.04.2018 and posted on 09.04.2018 by Pavel Pokhilko, Evgeny Epifanovsky, Anna I. Krylov
Using single precision floating point representation reduces the size of data and computation time by a factor of two relative to double precision conventionally used in electronic structure programs. For large-scale calculations, such as those encountered in many-body theories, reduced memory footprint alleviates memory and input/output bottlenecks. Reduced size of data can lead to additional gains due to improved parallel performance on CPUs and various accelerators. However, using single precision can potentially reduce the accuracy of computed observables. Here we report an implementation of coupled-cluster and equation-of-motion coupled-cluster methods with single and double excitations in single precision. We consider both standard implementation and one using Cholesky decomposition or resolution-of-the-identity of electron-repulsion integrals. Numerical tests illustrate that when single precision is used in correlated calculations, the loss of accuracy is insignificant and pure single-precision implementation can be used for computing energies, analytic gradients, excited states, and molecular properties. In addition to pure single-precision calculations, our implementation allows one to follow a single-precision calculation by clean-up iterations, fully recovering double-precision results while retaining significant savings.

Funding

AFOSR FA9550-16-1-0051

History

Email Address of Submitting Author

pokhilko@usc.edu

Institution

Department of Chemistry, University of Southern California; Q-Chem Inc.

Country

USA

ORCID For Submitting Author

0000-0001-5754-9836

Declaration of Conflict of Interest

no conflict of interest

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in Journal of Chemical Theory and Computation

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