what's the use of parameter mirror in caffe

[babala]

I have two questions?

1,what's the use of parameter mirror in caffe?

2,when I read the AlexNet I find that when the phase is Train,the parameter mirror is true.

when the phase is Test ,the parameter mirror is false. I wanna konw why?

[Jan C Peters]

I am not 100% sure, but to make an educated guess: It adds copies of samples to the training by mirroring existing images (which usually makes sense, since the class of the image is not affected by mirroring, but this gives more training data). This is of no significance in testing, so it is deactivated.

Jan

[Triet Chau]

It is random left-right flipping, a common operating when training models. Source: https://github.com/BVLC/caffe/issues/4469.
It would not add more data to your training set, I think