Coordinate Descent Quadratic Update

Problem

For the 1D restriction f(x) = 0.5 * a * x^2 - b * x with a > 0, the coordinate-wise minimizer is x* = b / a.

Given a and b, return the update.

Hint

Set the scalar derivative a x - b to zero.

case 1

in: [2,4]

expected: 2

case 2

in: [1,-3]

expected: -3

case 3

in: [0.5,1]

expected: 2

Starter codePython

def coordinate_descent_quadratic_update(a, b):
    # Your code here
    pass

3 test cases · run your code against them in the editor