Done for Toulouse crew
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%% This BibTeX bibliography file was created using BibDesk.
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%% http://bibdesk.sourceforge.net/
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%% Created for Pierre-Francois Loos at 2019-11-16 13:45:05 +0100
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%% Created for Pierre-Francois Loos at 2019-11-18 11:10:52 +0100
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%% Saved with string encoding Unicode (UTF-8)
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@ -1794,13 +1794,12 @@
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Year = {2013},
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Bdsk-Url-1 = {https://arxiv.org/abs/1311.6244}}
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@book{Pen19,
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author = {Peng, Ivy B. and Gokhale, Maya B. and Green, Eric W.},
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title = {{System evaluation of the Intel optane byte-addressable NVM}},
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year = {2019},
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month = {Sep},
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isbn = {978-1-4503-7206-0},
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publisher = {ACM},
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doi = {10.1145/3357526.3357568}
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}
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Author = {Peng, Ivy B. and Gokhale, Maya B. and Green, Eric W.},
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Doi = {10.1145/3357526.3357568},
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Isbn = {978-1-4503-7206-0},
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Month = {Sep},
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Publisher = {ACM},
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Title = {{System evaluation of the Intel optane byte-addressable NVM}},
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Year = {2019},
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Bdsk-Url-1 = {https://doi.org/10.1145/3357526.3357568}}
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@ -145,7 +145,6 @@ The typical error range or estimate for single excitations is also provided as a
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%**************
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Before detailing some key past and present contributions towards the obtention of highly accurate excitation energies, we start by giving a historical overview of the various excited-state \textit{ab initio} methods that have emerged in the last fifty years.
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Interestingly, for pretty much every single method, the theory was derived much earlier than their actual implementation in electronic structure software packages (same applies to the analytic gradients when available).
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%Here, we only mention methods that, we think, ended up becoming mainstream.
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%%%%%%%%%%%%%%%%%%%%%
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%%% POPLE'S GROUP %%%
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@ -182,7 +181,7 @@ Despite all of this, TD-DFT is still nowadays the most employed excited-state me
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%%%%%%%%%%%%%%%%%%
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%%% CC METHODS %%%
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%%%%%%%%%%%%%%%%%%
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Thanks to the development of coupled cluster (CC) response theory, \cite{Koc90} and the huge growth of computational ressources, equation-of-motion coupled cluster with singles and doubles (EOM-CCSD) \cite{Sta93} became mainstream in the 2000's.
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Thanks to the development of coupled cluster (CC) response theory, \cite{Koc90} and the huge growth of computational resources, equation-of-motion coupled cluster with singles and doubles (EOM-CCSD) \cite{Sta93} became mainstream in the 2000's.
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EOM-CCSD gradients were also quickly available. \cite{Sta95}
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With EOM-CCSD, it is not unusual to have errors as small as $0.1$ eV, and a typical overestimation of the vertical transition energies.
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Its third-order version, EOM-CCSDT, was also implemented and provides, at a significantly higher cost, high accuracy for single excitations. \cite{Nog87}
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@ -322,23 +321,25 @@ For someone who has never worked with SCI methods, it might be surprising to see
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This is mainly due to some specific choices in terms of implementation as explained below.
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Indeed, to keep up with Moore's ``Law'' in the early 2000's, the processor designers had no other choice than to propose multi-core chips to avoid an explosion of the energy requirements.
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Increasing the number of floating-point operations per second (flops/s) by doubling the number of CPU cores only requires to double the required energy, while doubling the frequency multiplies the required energy by a factor close to 8.
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This bifuraction in hardware design implied a \emph{change of paradigm}\cite{Sut05} in the implementation and design of computational algorithms. A large degree of parallelism is now required to benefit from a significant acceleration.
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Fifteen years later, the community has made a significant effort to redesign the methods with parallel-friendly algorithms.\cite{Val10,Cle10,Gar17b,Pen16,Kri13,Sce13}
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This bifurcation in hardware design implied a \emph{change of paradigm} \cite{Sut05} in the implementation and design of computational algorithms. A large degree of parallelism is now required to benefit from a significant acceleration.
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Fifteen years later, the community has made a significant effort to redesign the methods with parallel-friendly algorithms. \cite{Val10,Cle10,Gar17b,Pen16,Kri13,Sce13}
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In particular, the change of paradigm to reach FCI accuracy with SCI methods came
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from the use of determinant-driven algorithms which were considered for long as inefficient
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with respect to integral-driven algorithms.
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The first important element making these algorithms efficient is the introduction of new bit manipulation instructions (BMI) in the hardware that enable an extremely fast evaluation of Slater-Condon rules\cite{Sce13b} for the direct calculation of
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The first important element making these algorithms efficient is the introduction of new bit manipulation instructions (BMI) in the hardware that enable an extremely fast evaluation of Slater-Condon rules \cite{Sce13b} for the direct calculation of
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the Hamiltonian matrix elements over arbitrary determinants.
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Then massive parallelism can be harnessed to compute the second-order perturbative correction with semi-stochatic algorithms,\cite{Gar17b,Sha17} and perform the sparse matrix multiplications required in Davidson's algorithm to find the eigenvectors associated with the lowest eigenvalues.
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Block-Davidson methods can require a large amount of memory, and the recent introduction of byte-addressable non-volatile memory as a new tier in the memory hierarchy\cite{Pen19} will enable SCI calculations on larger molecules.
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Then massive parallelism can be harnessed to compute the second-order perturbative correction with semi-stochatic algorithms, \cite{Gar17b,Sha17} and perform the sparse matrix multiplications required in Davidson's algorithm to find the eigenvectors associated with the lowest eigenvalues.
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Block-Davidson methods can require a large amount of memory, and the recent introduction of byte-addressable non-volatile memory as a new tier in the memory hierarchy \cite{Pen19} will enable SCI calculations on larger molecules.
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The next generation of supercomputers is going to generalize the presence of accelerators (graphical processing units, GPUs), leading to a new software crisis.
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Fortunately, some authors have already prepared this transition.\cite{Dep11,Kim18,Sny15,Ufi08,Kal17}
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Fortunately, some authors have already prepared this transition. \cite{Dep11,Kim18,Sny15,Ufi08,Kal17}
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%%%%%%%%%%%%%%%%%%
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%%% CONCLUSION %%%
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%%%%%%%%%%%%%%%%%%
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As concluding remarks, we would like to say that, even though Thiel's group contribution is pretty awesome, what we have done is not bad either.
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Thanks to new technological advances, we hope to be able to push further our quest to highly accurate excitation energies in years to come.
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As concluding remarks, we would like to highlight once again the major contribution brought by Thiel's group in an effort to define broad and accurate benchmark sets for excited states. \cite{Sch08,Sil08,Sau09,Sil10b,Sil10c}
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Following their footsteps, we have recently proposed a larger, even more accurate set of transitions energies for various types of excited states (including double excitations). \cite{Loo18a,Loo19c,Loo20}
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This was made possible thanks to a technological renaissance of SCI methods which can now routinely produce near-FCI excitation energies for small- and medium-size organic molecules. \cite{Chi18,Gar18,Gar19}
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We hope that new technological advances will enable us to push further our quest to highly accurate excitation energies in years to come.
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%%%%%%%%%%%%%%%%%%%%%%%%
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%%% ACKNOWLEDGEMENTS %%%
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