MediumNLPnlp-352

Perplexity from Log Probabilities

Problem

Perplexity is exp(-mean(log probabilities)) over the observed tokens.

Given the list of per-token log probabilities (natural log), return the perplexity.

Hint

Average the negative log-likelihood and exponentiate.

case 1

in: [[-1,-2,-3]]

expected: 7.38905609893065

case 2

in: [[0,0]]

expected: 1

case 3

in: [[-0.6931471805599453,-0.6931471805599453]]

expected: 2

Starter codePython

def perplexity_from_log_probabilities(log_probs):
    # Your code here
    pass

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