see http://www.nec-labs.com/uploads/images/Department-Images/MediaAnalytics/papers/nips16_npairmetriclearning.pdf
Read `Improved Deep Metric Learning with Multi class N pair Loss Objective <http://www.nec-labs.com/uploads/images/Department-Images/MediaAnalytics/papers/nips16_npairmetriclearning.pdf>`_ .
Npair loss requires paired data. Npair loss has two parts, the first part is L2
regularizer on the embedding vector, the second part is cross entropy loss which
Npair loss requires paired data. Npair loss has two parts: the first part is L2
regularizer on the embedding vector; the second part is cross entropy loss which
takes the similarity matrix of anchor and positive as logits.
Args:
anchor(Variable): embedding vector for the anchor image. shape=[batch_size, embedding_dims]
positive(Variable): embedding vector for the positive image. shape=[batch_size, embedding_dims]
labels(Varieble): 1-D tensor. shape=[batch_size]
l2_res(float32): L2 regularization term on embedding vector, default: 0.02
labels(Variable): 1-D tensor. shape=[batch_size]
l2_reg(float32): L2 regularization term on embedding vector, default: 0.002