Steepest Descent Contraction Ratio

Problem

For a quadratic with smoothness L and strong convexity mu, the steepest descent method contracts the error by ((L - mu) / (L + mu))^2 per iteration.

Given L and mu with L > mu > 0, return this contraction factor.

Hint

It depends only on the condition number through the ratio of L - mu to L + mu.

case 1

in: [10,1]

expected: 0.6694214876033059

case 2

in: [4,2]

expected: 0.1111111111111111

case 3

in: [100,50]

expected: 0.1111111111111111

Starter codePython

def steepest_descent_contraction_ratio(l, mu):
    # Your code here
    pass

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