由于内部错误，无法在解释器上运行 tflite 模型

Question

我正在尝试为 Android 构建一个离线翻译器。我的模型深受本指南的启发： https: //www.tensorflow.org/tutorials/text/nmt_with_attention。我只是做了一些修改以确保模型是可序列化的。（您可以在最后找到模型的代码）

该模型在我的 jupyter 笔记本上完美运行。我使用的 Tensorflow 版本：2.3.0-dev20200617，我还能够使用以下代码片段生成 tflite 文件：

converter = tf.lite.TFLiteConverter.from_keras_model(partial_model)
tflite_model = converter.convert()

with tf.io.gfile.GFile('goog_nmt_v2.tflite', 'wb') as f:
  f.write(tflite_model)

但是，当我使用生成的 tflite 模型来获取 Android 上的预测时，它会抛出错误java.lang.IllegalArgumentException: Internal error: Failed to run on the given Interpreter: tensorflow/lite/kernels/concatenation.cc:73 t->dims->data[d] != t0->dims->data[d] (8 != 1) Node number 84 (CONCATENATION) failed to prepare.

这很奇怪，因为我提供了与我在 jupyter 笔记本中完全相同的输入尺寸。以下是用于测试（虚拟输入）模型是否在 Android 上运行的 java 代码：

 HashMap<Integer, Object> outputVal = new HashMap<>();
        for(int i=0; i<2; i++) outputVal.put(i, new float[1][5]);
        float[][] inp_test = new float[1][8];
        float[][] enc_hidden = new float[1][1024];
        float[][] dec_input = new float[1][1];
        float[][] dec_test = new float[1][8];

        tfLite.runForMultipleInputsOutputs(new Object[] {inp_test,enc_hidden, dec_input, dec_test},outputVal);

这是我的 gradle 依赖项：

dependencies {
    implementation fileTree(dir: 'libs', include: ['*.jar'])

    implementation 'androidx.appcompat:appcompat:1.1.0'
    implementation 'org.tensorflow:tensorflow-lite:0.0.0-nightly'
    implementation 'org.tensorflow:tensorflow-lite-select-tf-ops:0.0.0-nightly'
    // This dependency adds the necessary TF op support.
    implementation 'androidx.constraintlayout:constraintlayout:1.1.3'
    testImplementation 'junit:junit:4.12'
    androidTestImplementation 'androidx.test.ext:junit:1.1.1'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.2.0'
}

正如错误所指出的，节点 84 处的尺寸有问题。因此我继续使用 Netron 可视化 tflite 文件。我已经缩放了串联节点，您可以在此处找到节点的图片以及输入和输出尺寸。您可以在此处找到整个生成的图表。

事实证明，位置 84 处的串联节点实际上并未串联，您可以从输入和输出维度看到这一点。它只是在处理 1X1X1 和 1X1X256 矩阵后吐出 1X1X1 矩阵。我知道 tflite 图与原始模型图不同，因为许多操作被替换甚至删除以进行优化，但这似乎有点奇怪。

我无法将其与错误联系起来。如果它在 jupyter 上完美运行，是框架问题还是我遗漏了什么？另外，有人可以向我解释一下这个错误是t->dims->data[d] != t0->dims->data[d]什么意思吗？

如果您对任何一个问题有答案，请写下来。如果您需要任何额外的详细信息，请告诉我。

这是模型的代码：

Tx = 8
def Partial_model():
    outputs = []
    X = tf.keras.layers.Input(shape=(Tx,))
    partial = tf.keras.layers.Input(shape=(Tx,))
    enc_hidden = tf.keras.layers.Input(shape=(units,))
    dec_input = tf.keras.layers.Input(shape=(1,))
    
    d_i = dec_input
    e_h = enc_hidden
    X_i = X
    
    enc_output, e_h = encoder(X, enc_hidden)
    
    
    dec_hidden = enc_hidden
    print(dec_input.shape, 'inp', dec_hidden.shape, 'dec_hidd')
    for t in range(1, Tx):
        print(t, 'tt')
      # passing enc_output to the decoder
        predictions, dec_hidden, _ = decoder(d_i, dec_hidden, enc_output)
#         outputs.append(predictions)
        print(predictions.shape, 'pred')
        d_i = tf.reshape(partial[:, t], (-1, 1))
        print(dec_input.shape, 'dec_input')
    
    predictions, dec_hidden, _ = decoder(d_i, dec_hidden, enc_output)
    d_i = tf.squeeze(d_i)
    
    outputs.append(tf.math.top_k(predictions, 5))
    
    return tf.keras.Model(inputs = [X, enc_hidden, dec_input, partial], outputs = [outputs[0][0], outputs[0][1]])




class Encoder():
  def __init__(self, vocab_size, embedding_dim, enc_units, batch_sz):
    self.batch_sz = batch_sz
    self.enc_units = enc_units
    self.embedding = tf.keras.layers.Embedding(vocab_size, embedding_dim)
    self.gru = tf.keras.layers.GRU(self.enc_units,
                                   return_sequences=True,
                                   return_state=True,
                                   recurrent_initializer='glorot_uniform')

  def __call__(self, x, hidden):
    x = self.embedding(x)
    output, state = self.gru(x, initial_state = hidden)
    print(output.shape, hidden.shape, "out", "hid")
    return output, state


  def initialize_hidden_state(self):
    return tf.zeros((self.batch_sz, self.enc_units))



class BahdanauAttention():
  def __init__(self, units):
    self.W1 = tf.keras.layers.Dense(units)
    self.W2 = tf.keras.layers.Dense(units)
    self.V = tf.keras.layers.Dense(1)

  def __call__(self, query, values):
    # query hidden state shape == (batch_size, hidden size)
    # query_with_time_axis shape == (batch_size, 1, hidden size)
    # values shape == (batch_size, max_len, hidden size)
    # we are doing this to broadcast addition along the time axis to calculate the score
    print(query.shape, 'shape')
    query_with_time_axis = tf.expand_dims(query, 1)
    # score shape == (batch_size, max_length, 1)
    # we get 1 at the last axis because we are applying score to self.V
    # the shape of the tensor before applying self.V is (batch_size, max_length, units)
    print("2")
    score = self.V(tf.nn.tanh(
        self.W1(query_with_time_axis) + self.W2(values)))
    print("3")

    # attention_weights shape == (batch_size, max_length, 1)
    attention_weights = tf.nn.softmax(score, axis=1)

    # context_vector shape after sum == (batch_size, hidden_size)
    context_vector = attention_weights * values
    context_vector = tf.reduce_sum(context_vector, axis=1)
    
    return context_vector, attention_weights


class Decoder():
  def __init__(self, vocab_size, embedding_dim, dec_units, batch_sz):
    self.dec_units = dec_units
    self.embedding = tf.keras.layers.Embedding(vocab_size, embedding_dim)
    self.gru = tf.keras.layers.GRU(self.dec_units,
                                   return_sequences=True,
                                   return_state=True,
                                   recurrent_initializer='glorot_uniform')
    self.fc = tf.keras.layers.Dense(vocab_size)

    # used for attention
    self.attention = BahdanauAttention(self.dec_units)

  def __call__(self, x, hidden, enc_output):
    # enc_output shape == (batch_size, max_length, hidden_size)
    context_vector, attention_weights = self.attention(hidden, enc_output)
    
    print(context_vector.shape, 'c_v', attention_weights.shape, "attention_w")

    # x shape after passing through embedding == (batch_size, 1, embedding_dim)
    x = self.embedding(x)

    # x shape after concatenation == (batch_size, 1, embedding_dim + hidden_size)
    print(x.shape, 'xshape', context_vector.shape, 'context')
    expanded_dims = tf.expand_dims(context_vector, 1)
    x = tf.concat([expanded_dims, x], axis=-1)

    # passing the concatenated vector to the GRU
    output, state = self.gru(x)

    # output shape == (batch_size * 1, hidden_size)
    output = tf.reshape(output, (-1, output.shape[2]))

    # output shape == (batch_size, vocab)
    x = self.fc(output)

    return x, state, attention_weights

Answer 1

您可以在 python 笔记本中加载生成的 .tflite 文件，并传递与 Keras 模型相同的输入。您必须看到确切的输出，因为在模型转换过程中不会损失准确性。如果那里有问题...android操作时就会出现问题。如果没有……一切都会很好。使用 Tensorflow 指南中的以下代码在 Python 中运行推理：

import numpy as np
import tensorflow as tf

# Load the TFLite model and allocate tensors.
interpreter = tf.lite.Interpreter(model_path="converted_model.tflite")
interpreter.allocate_tensors()

# Get input and output tensors.
input_details = interpreter.get_input_details()
output_details = interpreter.get_output_details()

# Test the model on random input data.
input_shape = input_details[0]['shape']
input_data = np.array(np.random.random_sample(input_shape), dtype=np.float32)
interpreter.set_tensor(input_details[0]['index'], input_data)

interpreter.invoke()

# The function `get_tensor()` returns a copy of the tensor data.
# Use `tensor()` in order to get a pointer to the tensor.
output_data = interpreter.get_tensor(output_details[0]['index'])
print(output_data)

快乐编码！