InvalidArgumentError：loc 处需要可广播形状（未知）

背景

我对 Python 和机器学习完全陌生。我只是尝试根据在互联网上找到的代码建立一个 UNet，并希望将其适应我正在处理的情况。当试图.fit将UNet训练数据，我收到以下错误：

InvalidArgumentError:  required broadcastable shapes at loc(unknown)
     [[node Equal (defined at <ipython-input-68-f1422c6f17bb>:1) ]] [Op:__inference_train_function_3847]

当我搜索它时，我得到了很多结果，但大多数都是不同的错误。

这是什么意思？更重要的是，我该如何解决这个问题？

导致错误的代码

该错误的上下文如下： 我想分割图像并标记不同的类别。 我为训练、测试和验证数据设置了目录“trn”、“tst”和“val”。这dir_dat()功能适用os.path.join()获取各自的完整路径data set https://www.dropbox.com/sh/g4yr4qjgjtsytmi/AABJXVehoCw5In9wQvL7Llu2a?dl=0。这 3 个文件夹中的每一个都有每个类的子目录，并用整数标记。每个文件夹里都有一些.tif各个类别的图像。

我定义了以下图像数据生成器（训练数据稀疏，因此增强）：

classes = np.array([ 0,  2,  4,  6,  8, 11, 16, 21, 29, 30, 38, 39, 51])
bs = 15 # batch size

augGen = ks.preprocessing.image.ImageDataGenerator(rotation_range = 365,
                                                   width_shift_range = 0.05,
                                                   height_shift_range = 0.05,
                                                   horizontal_flip = True,
                                                   vertical_flip = True,
                                                   fill_mode = "nearest") \
    .flow_from_directory(directory = dir_dat("trn"),
                         classes = [str(x) for x in classes.tolist()],
                         class_mode = "categorical",
                         batch_size = bs, seed = 42)
    
tst_batches = ks.preprocessing.image.ImageDataGenerator() \
    .flow_from_directory(directory = dir_dat("tst"),
                         classes = [str(x) for x in classes.tolist()],
                         class_mode = "categorical",
                         batch_size = bs, shuffle = False)

val_batches = ks.preprocessing.image.ImageDataGenerator() \
    .flow_from_directory(directory = dir_dat("val"),
                         classes = [str(x) for x in classes.tolist()],
                         class_mode = "categorical",
                         batch_size = bs)

然后我根据以下内容设置了UNet这个例子 https://github.com/bnsreenu/python_for_microscopists/blob/master/074-Defining%20U-net%20in%20Python%20using%20Keras.py。在这里，我更改了一些参数以使 UNet 适应情况（多个类），即最后一层的激活和损失函数：

layer_in = ks.layers.Input(shape = (imgr, imgc, imgdim))
# convert pixel integer values to float
inVals = ks.layers.Lambda(lambda x: x / 255)(layer_in)

# Contraction path
c1 = ks.layers.Conv2D(16, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(inVals)
c1 = ks.layers.Dropout(0.1)(c1)
c1 = ks.layers.Conv2D(16, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(c1)
p1 = ks.layers.MaxPooling2D((2, 2))(c1)

c2 = ks.layers.Conv2D(32, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(p1)
c2 = ks.layers.Dropout(0.1)(c2)
c2 = ks.layers.Conv2D(32, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(c2)
p2 = ks.layers.MaxPooling2D((2, 2))(c2)
 
c3 = ks.layers.Conv2D(64, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(p2)
c3 = ks.layers.Dropout(0.2)(c3)
c3 = ks.layers.Conv2D(64, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(c3)
p3 = ks.layers.MaxPooling2D((2, 2))(c3)
 
c4 = ks.layers.Conv2D(128, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(p3)
c4 = ks.layers.Dropout(0.2)(c4)
c4 = ks.layers.Conv2D(128, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(c4)
p4 = ks.layers.MaxPooling2D(pool_size = (2, 2))(c4)
 
c5 = ks.layers.Conv2D(256, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(p4)
c5 = ks.layers.Dropout(0.3)(c5)
c5 = ks.layers.Conv2D(256, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(c5)

# Expansive path 
u6 = ks.layers.Conv2DTranspose(128, (2, 2), strides = (2, 2), padding = "same")(c5)
u6 = ks.layers.concatenate([u6, c4])
c6 = ks.layers.Conv2D(128, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(u6)
c6 = ks.layers.Dropout(0.2)(c6)
c6 = ks.layers.Conv2D(128, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(c6)
 
u7 = ks.layers.Conv2DTranspose(64, (2, 2), strides = (2, 2), padding = "same")(c6)
u7 = ks.layers.concatenate([u7, c3])
c7 = ks.layers.Conv2D(64, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(u7)
c7 = ks.layers.Dropout(0.2)(c7)
c7 = ks.layers.Conv2D(64, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(c7)
 
u8 = ks.layers.Conv2DTranspose(32, (2, 2), strides = (2, 2), padding = "same")(c7)
u8 = ks.layers.concatenate([u8, c2])
c8 = ks.layers.Conv2D(32, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(u8)
c8 = ks.layers.Dropout(0.1)(c8)
c8 = ks.layers.Conv2D(32, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(c8)
 
u9 = ks.layers.Conv2DTranspose(16, (2, 2), strides = (2, 2), padding = "same")(c8)
u9 = ks.layers.concatenate([u9, c1], axis = 3)
c9 = ks.layers.Conv2D(16, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(u9)
c9 = ks.layers.Dropout(0.1)(c9)
c9 = ks.layers.Conv2D(16, (3, 3), activation = "relu",
                            kernel_initializer = "he_normal", padding = "same")(c9)
 
out = ks.layers.Conv2D(1, (1, 1), activation = "softmax")(c9)
 
model = ks.Model(inputs = layer_in, outputs = out)
model.compile(optimizer = "adam", loss = "sparse_categorical_crossentropy", metrics = ["accuracy"])
model.summary()

最后，我定义了回调并运行了训练，这产生了错误：

cllbs = [
    ks.callbacks.EarlyStopping(patience = 4),
    ks.callbacks.ModelCheckpoint(dir_out("Checkpoint.h5"), save_best_only = True),
    ks.callbacks.TensorBoard(log_dir = './logs'),# log events for TensorBoard
    ]

model.fit(augGen, epochs = 5, validation_data = val_batches, callbacks = cllbs)

完整控制台输出

这是运行最后一行时的完整输出（如果它有助于解决问题）：

trained = model.fit(augGen, epochs = 5, validation_data = val_batches, callbacks = cllbs)
Epoch 1/5
Traceback (most recent call last):

  File "<ipython-input-68-f1422c6f17bb>", line 1, in <module>
    trained = model.fit(augGen, epochs = 5, validation_data = val_batches, callbacks = cllbs)

  File "c:\users\manuel\python\lib\site-packages\tensorflow\python\keras\engine\training.py", line 1183, in fit
    tmp_logs = self.train_function(iterator)

  File "c:\users\manuel\python\lib\site-packages\tensorflow\python\eager\def_function.py", line 889, in __call__
    result = self._call(*args, **kwds)

  File "c:\users\manuel\python\lib\site-packages\tensorflow\python\eager\def_function.py", line 950, in _call
    return self._stateless_fn(*args, **kwds)

  File "c:\users\manuel\python\lib\site-packages\tensorflow\python\eager\function.py", line 3023, in __call__
    return graph_function._call_flat(

  File "c:\users\manuel\python\lib\site-packages\tensorflow\python\eager\function.py", line 1960, in _call_flat
    return self._build_call_outputs(self._inference_function.call(

  File "c:\users\manuel\python\lib\site-packages\tensorflow\python\eager\function.py", line 591, in call
    outputs = execute.execute(

  File "c:\users\manuel\python\lib\site-packages\tensorflow\python\eager\execute.py", line 59, in quick_execute
    tensors = pywrap_tfe.TFE_Py_Execute(ctx._handle, device_name, op_name,

InvalidArgumentError:  required broadcastable shapes at loc(unknown)
     [[node Equal (defined at <ipython-input-68-f1422c6f17bb>:1) ]] [Op:__inference_train_function_3847]

Function call stack:
train_function

当类标签的数量与输出层的输出形状不匹配时，我遇到了这个问题。

例如，如果有 10 个类标签，并且我们将输出层定义为：

output = tf.keras.layers.Conv2D(5, (1, 1), activation = "softmax")(c9)

由于类标签的数量 (10) 不等于输出形状 (5）。 然后，我们就会得到这个错误。

确保类标签的数量与输出层的输出形状匹配。