Output Keras model 的尺寸

Question

我使用 ImageDataGenerator 加载我的训练数据

train_generator = train_datagen.flow_from_directory(
    directory= TRAIN_PATH,
    target_size=(224, 224),
    color_mode="rgb",
    batch_size=32,
    class_mode="categorical",
    shuffle=True,
    seed=42
)  

之后我收到一条消息

Found 6552 images belonging to 102 classes.

当我定义 model 的方式

model1 = MobileNetV2(include_top=False, input_shape=(224, 224, 3))
flat1 = Flatten()(model1.outputs)
class1 = Dense(1024, activation='relu')(flat1)
output = Dense(output_dim = 102, activation='softmax')(class1)
model = Model(inputs=model1.inputs, outputs=output)

model.compile(optimizer=keras.optimizers.Adam(),
              loss='sparse_categorical_crossentropy',
              metrics=['accuracy'])

history = model.fit_generator(
      train_generator,
      steps_per_epoch=100,
      epochs=100,
      verbose=2)

我有以下错误

ValueError: Error when checking target: expected dense_2 to have shape (1,) but got array with shape (102,)

但是我的 output 层的形状是 102。为什么会这样？

Answer 1

您可以简单地将损失从sparse_categorical_crossentropy更改为categorical_crossentropy来解决。

生成器中的“分类”模式将一次性编码标签，这不适合sparse_categorical_crossentropy