False positive rate at K recall

Question

I just stumbled upon a new metric I've never heard about called False Positive rate at K recall (FPR-K).
Searching the internet I just managed to find more papers using the metric but none of them actually explain how is it calculated.
The paper was on matching feature points in multi-modal images.

I know what is AP@K, used in tasks involving some thresholding (i.e. image detection where we're using intersection over union to calculate our TP/FP etc).

My assumption regarding FPR-95 is that there's some thresholding involved as well (else why the "at K" term?), and as with thresholds, they control the precision / recall rate. So we set a threshold causing 95% recall, and now we calculate the FP rate (FP / FP + TN).

Can anyone validate or invalidate my assumption?

Answer 1

I've found the answer in some paper.

FPR at 95% TPR can be interpreted as the probability that a negative (out-of-distribution) example is misclassified as positive (in-distribution) when the true positive rate (TPR) is as high as 95%.
True positive rate can be computed by TPR = TP / (TP+FN), where TP and FN denote true positives and false negatives respectively.
The false positive rate (FPR) can be computed by FPR = FP / (FP+TN), where FP and TN denote false positives and true negatives respectively.