Why number of labels has to be greater than 2 in MultiBoxTarget?

[nttstar]

I saw one piece of code in MultiBoxTarget.cu below:

const int num_labels = labels.size(1);
CHECK_GT(num_labels, 2);

But why? I think one or two ground truth boxes are also valid for training.

[zhreshold]

Just to make reuse of some temporary buffer without malloc new space.

[nttstar]

So we have to append '-1's if there are only 1 or 2 labels?

[zhreshold]

correct

[rkpandya]

I am also training on a different dataset and face this issue. Where do I append '-1'?