5.1. [sampling] section

Specify the parameters of the Monte Carlo (MC) sampling method, such as the number of replicas, the temperature range, and the number of Monte Carlo steps. The example is shown as follows.

[sampling]
nreplicas = 3
nprocs_per_replica = 1
kTstart = 500.0
kTend = 1500.0
nsteps = 5
RXtrial_frequency = 2
sample_frequency = 1
print_frequency = 1

5.1.1. Input Format

Specify a keyword and its value in the form keyword = value. Comments can also be entered by adding # (Subsequent characters are ignored).

5.1.2. Keywords

  • About sampling method

    • sampler

      Format : string

      Description : Relica exchange MC method (“RXMC”) or population annealing MC method (“PAMC”).

  • About temperatures

    • Specify temperature points by using kTs or kTstart, kTend, and kTnum (lineary spaced). If kTs is specified, the others will be ignored.

    • Temperatures should be given in the unit of Kelvin.

    • kTs

      Format : list of float (>0)

      Description : Temperature points. When sampler = "RXMC", the number of temperature points should equal to nreplicas.

    • kTstart

      Format : float (>0)

      Description : Minimum temperature.

    • kTend

      Format : float (>0)

      Description : Maximum temperature.

    • kTnum (Only for PAMC)

      Format : int (>0)

      Description : The number of temperature points. When sampler = "RXMC", the number of temperature points will equal to nreplicas.

    • linspace_in_beta

      Format : true or false

      Description : If true, temperature points are generated in the inverse temperature space with equal intervals. If false, temperature points are generated in the temperature space with equal intervals. Default value = false.

  • About replica

    • nprocs_per_replica

      Format : int (natural number)

      Description : The number of processes for the replica. Default value = 1.

    • nreplicas

      Format : int (natural number)

      Description : The number of replicas.

  • Others

    • nsteps

      Format : int (natural number)

      Description : Number of Monte Carlo steps.

    • nsteps_between_annealing (Only for sampler = "PAMC")

      Format : int (natural number)

      Description : Number of Monte Carlo steps for each temperature.

    • RXtrial_frequency (Only for sampler = "RXMC")

      Format : int (natural number)

      Description : The interval for performing replica exchange trials. For example, setting this value to 1 means that replica exchange is attempted at every Monte Carlo step, while setting this to 2 means that exchange is attempted at every second step. Default = 1.

    • resample_frequency (Only for sampler = "PAMC")

      Format : int (natural number)

      Description : The interval for performing replica resampling. For example, setting this value to 1 means that replica resampling is attempted after every temperature lowering, while setting this to 2 means that resampling is attempted at every second step. Default = 1.

    • sample_frequency

      Format : int (natural number)

      Description : The interval for observation of physical quantities. Default value = 1.

    • print_frequency

      Format : int (natural number)

      Description : The interval for saving physical quantities. Default value = 1.

    • reload

      Format : bool (“true” or “false”)

      Description : Whether to restart a prior calculation from the last step finished last time. Default value = false.

    • throw_out

      Format : int or float

      Description : The number (int) or ratio (float) of measurements to be thrown out as thermalization in the process of the evaluation of expectation values. Default value = 0.5 .

    • enable_grandcanonical

      Format : bool (“true” or “false”)

      Description : Whether to allow grand canonical sampling. Default value = false.

    • gc_ratio

      Format : float

      Description : The ratio of the grand canonical update that changes the number of elements among the trials of configuration updates, when the grand canonical sampling is turned on. Default value = 0.3 .