“Swarm relaxation”: Equilibrating a large ensemble of computer simulations

  • Shahrazad M. A. Malek
  • Richard K. Bowles
  • Ivan Saika-Voivod
  • Francesco Sciortino
  • Peter H. Poole
Regular Article
Part of the following topical collections:
  1. Advances in Computational Methods for Soft Matter Systems


It is common practice in molecular dynamics and Monte Carlo computer simulations to run multiple, separately-initialized simulations in order to improve the sampling of independent microstates. Here we examine the utility of an extreme case of this strategy, in which we run a large ensemble of M independent simulations (a “swarm”), each of which is relaxed to equilibrium. We show that if M is of order \(10^{3}\), we can monitor the swarm’s relaxation to equilibrium, and confirm its attainment, within \(\sim 10\bar{\tau}\), where \(\bar{\tau}\) is the equilibrium relaxation time. As soon as a swarm of this size attains equilibrium, the ensemble of M final microstates from each run is sufficient for the evaluation of most equilibrium properties without further sampling. This approach dramatically reduces the wall-clock time required, compared to a single long simulation, by a factor of several hundred, at the cost of an increase in the total computational effort by a small factor. It is also well suited to modern computing systems having thousands of processors, and is a viable strategy for simulation studies that need to produce high-precision results in a minimum of wall-clock time. We present results obtained by applying this approach to several test cases.

Graphical abstract


Topical issue: Advances in Computational Methods for Soft Matter Systems 


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Copyright information

© EDP Sciences, SIF, Springer-Verlag GmbH Germany, part of Springer Nature 2017

Authors and Affiliations

  • Shahrazad M. A. Malek
    • 1
  • Richard K. Bowles
    • 2
  • Ivan Saika-Voivod
    • 1
  • Francesco Sciortino
    • 3
  • Peter H. Poole
    • 4
  1. 1.Department of Physics and Physical OceanographyMemorial University of NewfoundlandSt. John’sCanada
  2. 2.Department of ChemistryUniversity of SaskatchewanSaskatoonCanada
  3. 3.Dipartimento di FisicaUniversità di Roma La SapienzaRomaItaly
  4. 4.Department of PhysicsSt. Francis Xavier UniversityAntigonishCanada

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