警告：tensorflow：模型是用形状 (20, 37, 42) 构建的，用于输入 Tensor(“input_5:0”, shape=(20, 37, 42), dtype=float32)，但是

Question

WARNING:tensorflow:Model was constructed with shape (20, 37, 42) for input Tensor("input_5:0", shape=(20, 37, 42), dtype=float32), but it was called on an input with incompatible shape (None, 37).

Hello! Deep learning noob here... I'm having trouble using LSTM layers. The input is a length 37 float array containing 2 floats and a length 35 one-hot array converted into float. The output is a length 19 array with 0s and 1s. Like the title suggests, I'm having trouble reshaping my input data to fit the model, and I'm not even sure what input dimensions would be considered 'compatible'

import numpy as np
import tensorflow as tf
from tensorflow import keras
from tensorflow.keras import layers


import random
inputs, outputs = [], []
for x in range(10000):
    tempi, tempo = [], []
    tempi.append(random.random() - 0.5)
    tempi.append(random.random() - 0.5)
    for x2 in range(35):
        if random.random() > 0.5:
            tempi.append(1.)
        else:
            tempi.append(0.)
    for x2 in range(19):
        if random.random() > 0.5:
            tempo.append(1.)
        else:
            tempo.append(0.)
    inputs.append(tempi)
    outputs.append(tempo)

batch = 20
timesteps = 42
training_units = 0.85

cutting_point_i = int(len(inputs)*training_units)
cutting_point_o = int(len(outputs)*training_units)
x_train, x_test = np.asarray(inputs[:cutting_point_i]), np.asarray(inputs[cutting_point_i:])
y_train, y_test = np.asarray(outputs[:cutting_point_o]), np.asarray(outputs[cutting_point_o:])

input_layer = keras.Input(shape=(37,timesteps),batch_size=batch)
dense = layers.LSTM(150, activation="sigmoid", return_sequences=True)
x = dense(input_layer)
hidden_layer_2 = layers.LSTM(150, activation="sigmoid", return_sequences=True)(x)
output_layer = layers.Dense(10, activation="softmax")(hidden_layer_2)
model = keras.Model(inputs=input_layer, outputs=output_layer, name="my_model"

Answer 1

Several problems here.

• Your input didn't have time steps, you need input shape (n, time steps, features)
• In input_shape , the time steps dimension comes first, not last
• Your last LSTM layer returned sequences, so you can't compare it with 0s and 1s

What I did:

• I added time steps to your data (7)
• I permuted the dimensions in input_shape
• I set the final return_sequences=False

Completely fixed example with generated data:

import numpy as np
from tensorflow import keras
from tensorflow.keras import layers

batch = 20
n_samples = 1000
timesteps = 7
features = 10

x_train = np.random.rand(n_samples, timesteps, features)
y_train = keras.utils.to_categorical(np.random.randint(0, 10, n_samples))

input_layer = keras.Input(shape=(timesteps, features),batch_size=batch)
dense = layers.LSTM(16, activation="sigmoid", return_sequences=True)(input_layer)
hidden_layer_2 = layers.LSTM(16, activation="sigmoid", return_sequences=False)(dense)
output_layer = layers.Dense(10, activation="softmax")(hidden_layer_2)
model = keras.Model(inputs=input_layer, outputs=output_layer, name="my_model")

model.compile(loss='categorical_crossentropy', optimizer='adam')

history = model.fit(x_train, y_train)

Train on 1000 samples
  20/1000 [..............................] - ETA: 2:50 - loss: 2.5145
 200/1000 [=====>........................] - ETA: 14s - loss: 2.3934 
 380/1000 [==========>...................] - ETA: 5s - loss: 2.3647 
 560/1000 [===============>..............] - ETA: 2s - loss: 2.3549
 740/1000 [=====================>........] - ETA: 1s - loss: 2.3395
 900/1000 [==========================>...] - ETA: 0s - loss: 2.3363
1000/1000 [==============================] - 4s 4ms/sample - loss: 2.3353

Answer 2

The correct input for your model is (20, 37, 42). Note: Here 20 is the batch_size you have explicitly specified.

Code:

import numpy as np
import tensorflow as tf
from tensorflow import keras
from tensorflow.keras import layers

batch = 20
timesteps = 42
training_units = 0.85

x1 = tf.constant(np.random.randint(50, size =(1000,37, 42)), dtype = tf.float32)
y1 = tf.constant(np.random.randint(10, size =(1000,)), dtype = tf.int32)
 

input_layer = keras.Input(shape=(37,timesteps),batch_size=batch)
dense = layers.LSTM(150, activation="sigmoid", return_sequences=True)
x = dense(input_layer)
hidden_layer_2 = layers.LSTM(150, activation="sigmoid", return_sequences=True)(x)
hidden_layer_3 = layers.Flatten()(hidden_layer_2)
output_layer = layers.Dense(10, activation="softmax")(hidden_layer_3)
model = keras.Model(inputs=input_layer, outputs=output_layer, name="my_model")

model.compile(optimizer='adam',
                  loss='sparse_categorical_crossentropy',
                  metrics=['accuracy'])
tf.keras.utils.plot_model(model, 'my_first_model.png', show_shapes=True)

Model Architecture:

You can clearly see the Input Size.

Code to Run:

model.fit(x = x1, y = y1, batch_size = batch, epochs = 10)

Note: Whatever batch_size you have specified you have to specify the same batch_size in the model.fit() command.

Output:

Epoch 1/10
50/50 [==============================] - 4s 89ms/step - loss: 2.3288 - accuracy: 0.0920
Epoch 2/10
50/50 [==============================] - 5s 91ms/step - loss: 2.3154 - accuracy: 0.1050
Epoch 3/10
50/50 [==============================] - 5s 101ms/step - loss: 2.3114 - accuracy: 0.0900
Epoch 4/10
50/50 [==============================] - 5s 101ms/step - loss: 2.3036 - accuracy: 0.1060
Epoch 5/10
50/50 [==============================] - 5s 99ms/step - loss: 2.2998 - accuracy: 0.1000
Epoch 6/10
50/50 [==============================] - 4s 89ms/step - loss: 2.2986 - accuracy: 0.1170
Epoch 7/10
50/50 [==============================] - 4s 84ms/step - loss: 2.2981 - accuracy: 0.1300
Epoch 8/10
50/50 [==============================] - 5s 103ms/step - loss: 2.2950 - accuracy: 0.1290
Epoch 9/10
50/50 [==============================] - 5s 106ms/step - loss: 2.2960 - accuracy: 0.1210
Epoch 10/10
50/50 [==============================] - 5s 97ms/step - loss: 2.2874 - accuracy: 0.1210