HardNLPnlp-305

chrF3 Character N-gram F-score

Problem

Compute a chrF3 score using character n-grams of order 1, 2, and 3. For each order, compute the clipped character n-gram F-score between candidate and reference, then return the arithmetic mean over orders.

An order where exactly one side lacks n-grams scores 0.0, an order where both sides lack n-grams is skipped, and 0.0 is returned when no order is scored. Return 0.0 when there are no matches at any scored order.

Hint

Average the per-order clipped F-scores, skipping only orders where both strings are too short.

Test cases

case 1

in: ["abc","abc"]

expected: 1

case 2

in: ["abc","abd"]

expected: 0.38888888888888884

case 3

in: ["ab","a"]

expected: 0.3333333333333333

case 4

in: ["",""]

expected: 0

case 5

in: ["a","b"]

expected: 0

Starter codePython

def chrf3(candidate, reference):
    # Your code here
    pass

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