AI說書 - 從0開始 - 262 | SHAP 數學實作

我想要一天分享一點「LLM從底層堆疊的技術」，並且每篇文章長度控制在三分鐘以內，讓大家不會壓力太大，但是又能夠每天成長一點。

有了 AI說書 - 從0開始 - 261 | SHAP 數學計算 的數學，我們來撰寫實作程式：

import itertools

words = {'I': 0.2, 'love': 0.6, 'playing': 0.5, 'chess': 0.4, 'with': 0.1, 'my': 0.3, 'friends': 0.4}
bonus = {('I', 'love'): 0.3, ('love', 'playing'): 0.25, ('playing', 'chess'): 0.45, ('with', 'my', 'friends'): 0.35}


def total_score(coalition):
	score = sum(words[word] for word in coalition)
	for b in bonus.keys():
		if all(word in coalition for word in b):
			score += bonus[b]
	return score
	

def shapley_value(word):
	N = len(words)
	permutations = list(itertools.permutations(words))
	marginal_contributions = []
	counter = 0
	for permutation in permutations:
		index = permutation.index(word)
		coalition_without_word = permutation[:index]
		coalition_with_word = permutation[:index+1]
		marginal_contribution = total_score(coalition_with_word) - total_score(coalition_without_word)
		marginal_contributions.append(marginal_contribution)
		counter += 1
	print(f"Processed {counter} permutations")
	return sum(marginal_contributions)
	

for word in words:
	print(f"The Shapley value of '{word}' is {shapley_value(word)}")