Root Dirichlet Concentration

Problem

Compute the Dirichlet concentration AlphaZero uses for root exploration noise.

The standard choice is alpha = 10 / n_legal_moves, so the noise stays proportional to the number of available moves. A non-positive move count returns 0.0.

Hint

Small concentrations concentrate the noise on a few moves; large ones spread it.

Test cases

case 1

in: [10]

expected: 1

case 2

in: [1]

expected: 10

case 3

in: [0]

expected: 0

case 4

in: [4]

expected: 2.5

Starter codePython

def root_dirichlet_concentration(n_legal_moves):
    # Your code here
    pass

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