.... Algorithmic Expert At a given AL state, the algorithmic expert selects a reasonable batch from the pool, D unl via: where m b b b φ φ φ denotes the underlying NMT model φ further retrained by incorporating the batch b b b, and B B B denotes the possible batches from D unl .
the number of possible batches is exponential in the size D unl , hence the above optimisation procedure would be very slow even for a moderately-sized pool.