hoomd.variant¶

Overview

`hoomd.variant.Constant`	A constant value.
`hoomd.variant.Cycle`	A cycle of linear ramps.
`hoomd.variant.Power`	A approach from initial to final value of x ^ (power).
`hoomd.variant.Ramp`	A linear ramp.
`hoomd.variant.Variant`	Variant base class.

Details

Define quantities that vary over the simulation.

A Variant object represents a scalar function of the time step. Some Operations accept Variant values for certain parameters, such as the kT parameter to NVT.

class hoomd.variant.Constant(value)¶

A constant value.

Parameters: value (float) – The value.

Constant returns value at all time steps.

value¶

The value.

Type: float

class hoomd.variant.Cycle(A, B, t_start, t_A, t_AB, t_B, t_BA)¶

A cycle of linear ramps.

Parameters

A (float) – The first value.
B (float) – The second value.
t_start (int) – The start time step.
t_A (int) – The hold time at the first value.
t_AB (int) – The time spent ramping from A to B.
t_B (int) – The hold time at the second value.
t_BA (int) – The time spent ramping from B to A.

Cycle holds the value A until time t_start. It continues holding that value until t_start + t_A. Then it ramps linearly from A to B over t_AB steps and holds the value B for t_B steps. After this, it ramps back from B to A over t_BA steps and repeats the cycle starting with t_A. Cycle repeats this cycle indefinitely.

A¶

The first value.

Type: float

B¶

The second value.

Type: float

t_start¶

The start time step.

Type: int

t_A¶

The holding time at A.

Type: int

t_AB¶

The time spent ramping from A to B.

Type: int

t_B¶

The holding time at B.

Type: int

t_BA¶

The time spent ramping from B to A.

Type: int

class hoomd.variant.Power(A, B, power, t_start, t_ramp)¶

A approach from initial to final value of x ^ (power).

Parameters

A (float) – The start value.
B (float) – The end value.
power (float) – The power of the approach to B.
t_start (int) – The start time step.
t_ramp (int) – The length of the ramp.

Power holds the value A until time t_start. Then it progresses at \(x^{power}\) from A to B over t_ramp steps and holds the value B after that.

p = Power(2, 8, 1 / 10, 10, 20)

A¶

The start value.

Type: float

B¶

The end value.

Type: float

power¶

The power of the approach to B.

Type: float

t_start¶

The start time step.

Type: int

t_ramp¶

The length of the ramp.

Type: int

class hoomd.variant.Ramp(A, B, t_start, t_ramp)¶

A linear ramp.

Parameters

A (float) – The start value.
B (float) – The end value.
t_start (int) – The start time step.
t_ramp (int) – The length of the ramp.

Ramp holds the value A until time t_start. Then it ramps linearly from A to B over t_ramp steps and holds the value B.

A¶

The start value.

Type: float

B¶

The end value.

Type: float

t_start¶

The start time step.

Type: int

t_ramp¶

The length of the ramp.

Type: int

class hoomd.variant.Variant¶

Variant base class.

Variants define values as a function of the simulation time step. Use one of the built in types or define your own custom function:

class CustomVariant(hoomd.variant.Variant):
    def __init__(self):
        hoomd.variant.Variant.__init__(self)

    def __call__(self, timestep):
        return (float(timestep)**(1 / 2))

__call__(timestep)¶

Evaluate the function.

Parameters: timestep (int) – The time step.
Returns: The value of the function at the given time step.
Return type: float