TimeDelay

class brainpy.math.TimeDelay(delay_target, delay_len, before_t0=None, t0=0.0, dt=None, name=None, interp_method='linear_interp')

Delay variable which has a fixed delay time length.

For example, we create a delay variable which has a maximum delay length of 1 ms

>>> import brainpy.math as bm
>>> delay = bm.TimeDelay(bm.zeros(3), delay_len=1., dt=0.1)
>>> delay(-0.5)
[-0. -0. -0.]

This function supports multiple dimensions of the tensor. For example,

1. the one-dimensional delay data

>>> delay = bm.TimeDelay(bm.zeros(3), delay_len=1., dt=0.1, before_t0=lambda t: t)
>>> delay(-0.2)
[-0.2 -0.2 -0.2]

2. the two-dimensional delay data

>>> delay = bm.TimeDelay(bm.zeros((3, 2)), delay_len=1., dt=0.1, before_t0=lambda t: t)
>>> delay(-0.6)
[[-0.6 -0.6]
 [-0.6 -0.6]
 [-0.6 -0.6]]

3. the three-dimensional delay data

>>> delay = bm.TimeDelay(bm.zeros((3, 2, 1)), delay_len=1., dt=0.1, before_t0=lambda t: t)
>>> delay(-0.8)
[[[-0.8]
  [-0.8]]
 [[-0.8]
  [-0.8]]
 [[-0.8]
  [-0.8]]]

Parameters:

• delay_target (Union[Array, Array]) – The initial delay data.

• t0 (Union[float, int]) – The zero time.

• delay_len (Union[float, int]) – The maximum delay length.

• dt (Union[float, int]) – The time precesion.

• before_t0 (Union[Callable, Array, Array, float, int]) –

  The delay data before ::math`t_0`. - when before_t0 is a function, it should receive a time argument t - when before_to is a tensor, it should be a tensor with shape

  of \((num_delay, ...)\), where the longest delay data is aranged in the first index.

• name (str) – The delay instance name.

• interp_method (str) –

  The way to deal with the delay at the time which is not integer times of the time step. For exameple, if the time step dt=0.1, the time delay length delay\_len=1., when users require the delay data at t-0.53, we can deal this situation with the following methods:

  • "linear_interp": using linear interpolation to get the delay value at the required time (default).

  • "round": round the time to make it is the integer times of the time step. For the above situation, we will use the time at t-0.5 to approximate the delay data at t-0.53.

  Added in version 2.1.1.

See also

LengthDelay

reset(delay_target, delay_len, t0=0.0, before_t0=None)

Reset the delay variable.

Parameters:

• delay_target (ArrayType) – The delay target.

• delay_len (float, int) – The maximum delay length. The unit is the time.

• t0 (Union[float, int]) – The zero time.

• before_t0 (callable, int, float, ArrayType) –

  The data before t0. - when before_t0 is a function, it should receive a time argument t

  (mirroring the behaviour of __init__).

  • when before_t0 is a tensor / numerical value, it is broadcast into the delay data before t0.