hpmc.tune

Overview

MoveSize

Tunes HPMCIntegrator move sizes to targeted acceptance rate.

Details

Tuners for HPMC.

class hoomd.hpmc.tune.MoveSize(trigger, moves, target, solver, types=None, max_move_size=None)

Tunes HPMCIntegrator move sizes to targeted acceptance rate.

Direct instantiation of this class requires a hoomd.tune.SolverStep that determines how move sizes are updated. This class also provides class methods to create a MoveSize tuner with built-in solvers; see MoveSize.secant_solver and MoveSize.scale_solver.

Parameters
  • trigger (hoomd.trigger.Trigger) – Trigger to determine when to run the tuner.

  • moves (list[str]) – A list of types of moves to tune. Available options are 'a' and 'd'.

  • target (float) – The acceptance rate for trial moves that is desired. The value should be between 0 and 1.

  • solver (hoomd.tune.SolverStep) – A solver that tunes move sizes to reach the specified target.

  • types (list[str]) – A list of string particle types to tune the move size for, defaults to None which upon attaching will tune all types in the system currently.

  • max_translation_move (float) – The maximum value of a translational move size to attempt \([\mathrm{length}]\).

  • max_rotation_move (float) – The maximum value of a rotational move size to attempt.

trigger

Trigger to determine when to run the tuner.

Type

hoomd.trigger.Trigger

moves

A list of types of moves to tune. Available options are 'a' and 'd'.

Type

list[str]

target

The acceptance rate for trial moves that is desired. The value should be between 0 and 1.

Type

float

solver

A solver that tunes move sizes to reach the specified target.

Type

hoomd.tune.SolverStep

types

A list of string particle types to tune the move size for, defaults to None which upon attaching will tune all types in the system currently.

Type

list[str]

max_translation_move

The maximum value of a translational move size to attempt \([\mathrm{length}]\).

Type

float

max_rotation_move

The maximum value of a rotational move size to attempt.

Type

float

Note

Limiting the maximum move sizes can lead to the inability to converge to the desired acceptance rate. Also, not limiting the move size can lead to move sizes that require the use of multiple periodic images to check for overlaps, especially in low density systems since the acceptance rate tends towards 1. Therefore, it is recommended to pick a moderate maximum move size for at least the translational moves to prevent requiring checking periodic images.

Note

In systems containing disparate particle shapes and/or sizes, move sizes for the different types should be tuned independently so that the acceptances rates for the different particles are each near the target acceptance ratio. Otherwise, the global acceptance ratio, a weighted average of the acceptance ratios for each individual particle type, will approach the target value, while the per-type acceptance ratios may not be close to the target value. This requires setting the types attribute to be one type at a time while setting the ignore_statistics flag of the shape property of the HPMC integrator for all other types to True.

property tuned

Whether or not the moves sizes have converged to the desired acceptance rate.

Type

bool

classmethod scale_solver(trigger, moves, target, types=None, max_translation_move=None, max_rotation_move=None, max_scale=2.0, gamma=1.0, tol=0.01)

Create a MoveSize tuner with a hoomd.tune.ScaleSolver.

Parameters
  • trigger (hoomd.trigger.Trigger) – Trigger to determine when to run the tuner.

  • moves (list[str]) – A list of types of moves to tune. Available options are 'a' and 'd'.

  • target (float) – The acceptance rate for trial moves that is desired. The value should be between 0 and 1.

  • types (list[str]) – A list of string particle types to tune the move size for, defaults to None which upon attaching will tune all types in the system currently.

  • max_translation_move (float) – The maximum value of a translational move size to attempt \([\mathrm{length}]\).

  • max_rotation_move (float) – The maximum value of a rotational move size to attempt.

  • max_scale (float) – Maximum scale factor.

  • gamma (float) – The value of gamma to pass through to hoomd.tune.ScaleSolver. Controls the size of corrections to the move size (larger values increase stability while increasing convergence time).

  • tol (float) – The absolute tolerance to allow between the current acceptance rate and the target before the move sizes are considered tuned. The tolerance should not be too much lower than the default of 0.01 as acceptance rates can vary significantly at typical tuning rates.

classmethod secant_solver(trigger, moves, target, types=None, max_translation_move=None, max_rotation_move=None, gamma=0.8, tol=0.01)

Create a MoveSize tuner with a hoomd.tune.SecantSolver.

This solver can be faster than hoomd.tune.ScaleSolver, but depending on the system slightly less stable. In general, with the default value of gamma this should not be a problem.

Parameters
  • trigger (hoomd.trigger.Trigger) – Trigger to determine when to run the tuner.

  • moves (list[str]) – A list of types of moves to tune. Available options are 'a' and 'd'.

  • target (float) – The acceptance rate for trial moves that is desired. The value should be between 0 and 1.

  • types (list[str]) – A list of string particle types to tune the move size for, defaults to None which upon attaching will tune all types in the system currently.

  • max_translation_move (float) – The maximum value of a translational move size to attempt, defaults to None which represents no maximum move size \([\mathrm{length}]\).

  • max_rotation_move (float) – The maximum value of a rotational move size to attempt, defaults to None which represents no maximum move size.

  • gamma (float) – The value of gamma to pass through to hoomd.tune.SecantSolver. Controls the size of corrections to the move size (smaller values increase stability). Should be between 0 and 1, defaults to 0.8.

  • tol (float) – The absolute tolerance to allow between the current acceptance rate and the target before the move sizes are considered tuned. The tolerance should not be too much lower than the default of 0.01 as acceptance rates can vary significantly at typical tuning rates.

Note

Increasing gamma towards 1 does not necessarily speed up convergence and can slow it down. In addition, large values of gamma can make the solver unstable, especially when tuning frequently.