BERTClassifier.swift

// Copyright 2020 The TensorFlow Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//     http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

// Adapted from: https://gist.github.com/eaplatanios/eae9c1b4141e961c949d6f2e7d424c6f
// Untested.

import Datasets
import ModelSupport
import TensorFlow

public struct BERTClassifier: Module, Regularizable {
  public var bert: BERT
  public var dense: Dense<Float>

  public var regularizationValue: TangentVector {
    TangentVector(
      bert: bert.regularizationValue,
      dense: dense.regularizationValue)
  }

  public init(bert: BERT, classCount: Int) {
    self.bert = bert
    self.dense = Dense<Float>(inputSize: bert.hiddenSize, outputSize: classCount)
  }

  /// Returns: logits with shape `[batchSize, classCount]`.
  @differentiable(wrt: self)
  public func callAsFunction(_ input: TextBatch) -> Tensor<Float> {
    dense(bert(input)[0..., 0])
  }
}