CASINO manual - Theory of Condensed Matter

1 Introduction
casino is a computer program system for performing quantum Monte Carlo (QMC) electronic structure
calculations that has been developed by members of the Theory of Condensed Matter group in
the Cambridge University physics department, and their collaborators, over more than 20 years. It is
capable of calculating incredibly accurate solutions to the Schrödinger equation of quantum mechanics
for realistic systems built from atoms.
Other highly accurate methods are known that can do this of course, but what makes casino important
is that given a big enough computer it can carry on doing this for systems containing hundreds or
even thousands of atoms. These many atoms can form isolated giant molecules or groups of molecules,
or they can be the repeating unit in an infinite crystal periodic in one, two, or three dimensions. Because
of their inferior scaling with system size, competing methods of comparable accuracy generally
struggle to handle more than a few tens of atoms. casino is also important because QMC is one of
the few methods genuinely capable of exploiting the power of modern computer hardware. Modern
versions of casino, by contrast, have been shown to exhibit essentially perfect parallel efficiency on
machines with hundreds of thousands of cores in all of its various modes of operation.
The QMC research program that culminated in casino as we know it today was begun in the early
1990s by Richard Needs, who had obtained inspiration from a short period working in the United
States. He developed his initial ideas in collaboration with Guna Rajagopal and Matthew Foulkes
and a number of early postdocs and students. Their initial test codes were gathered together and
generalized into the first QMC program capable of treating any arbitrary system (named ‘casino’
after a suggestion from Paul Kent) by Mike Towler, who had arrived in Cambridge in late 1996.
The first public version of casino was published in 1999. Absolutely fundamental improvements and
generalizations of the code were made by Neil Drummond (from 2002) and Pablo López Ríos (from
2004). Needs, Towler, Drummond and López Ríos are now considered to be principal authors of the
code, and all four of them continue to be at the heart of the project today.
Over the years, valuable additional contributions to the software base have been made by students,
postdocs, and other people working in collaboration with us. A reasonably complete set would include
Andrew Porter, Randy Hood, Andrew Williamson, Dario Alfè, Gavin Brown, Chris Pickard,
Rene Gaudoin, Ben Wood, Zoltán Radnai, Andrea Ma, Ryo Maezono, John Trail, Paul Kent, Nick
Hine, Alexander Badinski, Matthew Brown, Ken Esler, Andrew Morris, Norbert Nemec, Robert Lee,
Priyanka Seth, Bohshiang Jong, Lucian Anton, Katie Schwarz, Pascal Bugnion, and Elaheh Mostaani.
The following citation (quoted in full) is required in any publication describing results obtained with
casino:
R. J. Needs, M. D. Towler, N. D. Drummond and P. López Ríos, J. Phys.: Condens. Matter 22, 023201
(2010).
Further public information and resources—including forms for downloading the code—are available
at the casino web page:
http://vallico.net/casinoqmc
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