helper.update_odometer

Update odometer.

Module Contents

Functions

update_odometer(old_ind, upper_lim)

Increase a vector as odometer.
helper.update_odometer.update_odometer(old_ind, upper_lim)

Increase a vector as odometer.

Increases the last entry of the vector old_ind by 1, unless that would make it larger than the last entry of the vector upper_lim. In this case, it sets the last entry to 0 and instead increases the second-last entry of old_ind, unless that would make it larger than the second-last entry of upper_lim. In this case, it sets the second-last entry to 0 and instead increases the third-last entry of old_ind (and so on; it works like an odometer).

This function is useful when you want to have k nested loops, but k isn’t specified beforehand. For example, instead of looping over i and j going from 1 to 3, you could loop over a single variable going from 1 to 3^2 and set [i, j] = update_odometer([i, j], [3, 3]) at each step within the loop.

This function is adapted from QETLAB [1].

Examples

>>> from toqito.helper import update_odometer
>>> import numpy as np
>>> vec = np.array([0, 0])
>>> upper_lim = np.array([3, 2])
>>> for j in range(0, np.prod(upper_lim)-1):
...     vec = update_odometer(vec, upper_lim)
...     vec
array([0, 1])
array([1, 0])
array([1, 1])
array([2, 0])
array([2, 1])

References

[1]

Nathaniel Johnston. QETLAB: A MATLAB toolbox for quantum entanglement. https://github.com/nathanieljohnston/QETLAB. doi:10.5281/zenodo.44637.

Parameters:

  • old_ind (list[int] | numpy.ndarray) – The initial vector.

  • upper_lim (list[int] | numpy.ndarray) – The upper limit on which to increase the odometer to.

Returns:

The updated vector.

Return type:

list[int]