qml.math.ceil_log2¶

Compute the ceiling of the base-2 logarithm of an integer, with integer as output data type.

Parameters:: n (int) – Integer to compute the rounded-up base-2 logarithm of.
Returns:: Rounded-up base-2 logarithm of n.
Return type:: int

Example

On powers of two, ceil_log2 simply acts like np.log2 whose result was converted to an int:

>>> qml.math.ceil_log2(8)
3

On other numbers, the rounding of the logarithm becomes visible:

>>> qml.math.log2(14)
3.807354922057604
>>> qml.math.ceil_log2(14)
4

Note that we always round up:

>>> qml.math.round(qml.math.log2(9))
3.0
>>> qml.math.ceil_log2(9)
4

code/api/pennylane.math.ceil_log2

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