An instance of the class BdSimulator<D> in namespace Pscf::Rpc (for pscf_pc) or Pscf::Rpg (for pscf_pg) contains all of the algorithms and parameters that are needed to enable a partial saddle-point field theoretic simulation (PS-FTS) using Brownian dynamic sampling, but that are not needed for self-consistent field (SCFT) calculation. The associated parameter file block is one of two possible options (BdSimulator or McSimulator) for the optional, selectable "Simulator" subblock of the main System block of the parameter file.

Parameter File

The format of a BdSimulator parameter file block is given below in skeleton form:

BdSimulator{
  seed* int
  BdStep#*{ ... }
  Compressor#*{ ... }
  Perturbation#*{ ... }
  Ramp#*{ ... }
  AnalyzerManager*{ ... }
}

Here, as elsewhere in this documentation, the suffix # after a subblock name indicates a selectable subblock, and a * star after any parameter file element indicates an optional element. Every element of this block is formally optional, but particular commands (such as the SIMULATE) command require the presence of a minimal set of elements.

Each allowed element of a BdSimulator block is described in more detail below:

seed*	Optional random seed, which must be a positive integer. If no seed is set, the random number generator will be initialized using a seed generated from the system clock. (optional)
BdStep#*	The BdStep block prescribes an algorithm for a Brownian dynamics setp, and gives values for the step size and any other parameters required by that algorithm. (selectable and optional)
Compressor#*	A Compressor is an iterative solver that adjusts the pressure-like chemical potential field component in order to satisfy the mean-field incompressibility constraint, thus satisfying the partial-saddle point criterion. (selectable and optional)
Perturbation#*	An optional Perturbation block defines an additive perturbation of the field theoretic Hamiltonian, as for, e.g., the Einstein crystal thermodynamic integration method. (selectable and optional)
Ramp#*	An optional Ramp block initializes an algorithm to continuously change one or more system parameters during the course of a simulation. Though this is coded as an optional selectable block, the only option that is currently implemented is a LinearRamp that causes one or more parameters to vary linearly with BD step index. (selectable and optional)
AnalyzerManager#*	The optional AnalyzerManager block contains one or more subblocks that each initialize an analyzer algorithm. Each each analyzer implements a data analysis and/or data output operation that will be carried out periodically during a simulation (on-the-fly) or during analysis of a field trajectory file (postprocessing). (optional).

Relationships among subblocks of BdSimulator:

The BdStep and Compressor blocks must both be present in order to perform a BD simulation (command SIMULATE). Both of these elements may be omitted, however, from a parameter file that is used to initialize postprocessing of a field trajectory file.
If a BdStep is present, the Compressor block is required.
A Ramp is allowed only if a BdStep and Compressor are present, since these are algorithms that are only used during a simulation.
The AnalyzerManager block must be present in order to postprocess a trajectory file (command ANALYZE).

See also