FastText recall is 'nan' but precision is a number

问题

I trained a supervised model in FastText using the Python interface and I'm getting weird results for precision and recall.

First, I trained a model:

model = fasttext.train_supervised("train.txt", wordNgrams=3, epoch=100, pretrainedVectors=pretrained_model)

Then I get results for the test data:

def print_results(N, p, r):
    print("N\t" + str(N))
    print("P@{}\t{:.3f}".format(1, p))
    print("R@{}\t{:.3f}".format(1, r))

print_results(*model.test('test.txt'))

But the results are always odd, because they show precision and recall @1 as identical, even for different datasets, e.g. one output is:

N   46425
P@1 0.917
R@1 0.917

Then when I look for the precision and recall for each label, I always get recall as 'nan':

print(model.test_label('test.txt'))

And the output is:

{'__label__1': {'precision': 0.9202150724134941, 'recall': nan, 'f1score': 1.8404301448269882}, '__label__5': {'precision': 0.9134956983264135, 'recall': nan, 'f1score': 1.826991396652827}}

Does anyone know why this might be happening?

P.S.: To try a reproducible example of this behavior, please refer to https://github.com/facebookresearch/fastText/issues/1072 and run it with FastText 0.9.2

回答1:

It looks like FastText 0.9.2 has a bug in the computation of recall, and that should be fixed with this commit.

Installing a "bleeding edge" version of FastText e.g. with

pip install git+https://github.com/facebookresearch/fastText.git@b64e359d5485dda4b4b5074494155d18e25c8d13 --quiet

and rerunning your code should allow to get rid of the nan values in the recall computation.

来源：https://stackoverflow.com/questions/61787119/fasttext-recall-is-nan-but-precision-is-a-number