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Logarithm of the sum of exponentiations of the inputs in base-2 in Numpy
To get the Logarithm of the sum of exponentiations of the inputs in base 2, use the numpy.logaddexp() method in Python Numpy.
Calculates log2(2**x1 + 2**x2). This function is useful in machine learning when the calculated probabilities of events may be so small as to exceed the range of normal floating-point numbers. In such cases the base-2 logarithm of the calculated probability can be used instead. This function allows adding probabilities stored in such a fashion.
NumPy offers comprehensive mathematical functions, random number generators, linear algebra routines, Fourier transforms, and more. It supports a wide range of hardware and computing platforms, and plays well with distributed, GPU, and sparse array libraries.
Steps
At first, import the required library −
import numpy as np
Log2 input −
one = np.log2(2e-50) two = np.log2(3.2e-50)
Display the log input −
print("Value 1...\n", one)
print("Value 2...\n", two)To get the Logarithm of the sum of exponentiations of the inputs in base 2, use the numpy.logaddexp() method −
res = np.logaddexp(one, two)
print("\nLogarithm of the sum of exponentiations of the inputs in base 2...\n",res)Example
import numpy as np
# Calculates log2(2**x1 + 2**x2).
# This function is useful in machine learning when the calculated probabilities of events may be so small
# as to exceed the range of normal floating point numbers.
# In such cases the base-2 logarithm of the calculated probability can be used instead.
# This function allows adding probabilities stored in such a fashion.
# Log2 input
one = np.log2(2e-50)
two = np.log2(3.2e-50)
# Display the log input
print("Value 1...\n", one)
print("Value 2...\n", two)
# To get the Logarithm of the sum of exponentiations of the inputs in base 2, use the numpy.logaddexp() method in Python Numpy
res = np.logaddexp(one, two)
print("\nLogarithm of the sum of exponentiations of the inputs in base 2...\n",res)Output
Value 1... -165.09640474436813 Value 2... -164.41833283925547 Logarithm of the sum of exponentiations of the inputs in base 2... -164.00781734564688
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