[英]Load keras model with custom_metrics and custom loss
我通过子类 keras.model 创建了一个 keras model。 我还使用了自定义损失(焦点损失)、自定义指标(子类 keras.metrics)和学习率衰减。 我已经训练了 model 并使用tf.keras.callbacks.ModelCheckpoint(model_path)
保存了它。
当我尝试加载 model 时,我收到一条错误消息,显示ValueError: Unable to restore custom object of type _tf_keras_metric currently. Please make sure that the layer implements get_config and from_config when saving. In addition, please use the custom_objects arg when calling load_model()
ValueError: Unable to restore custom object of type _tf_keras_metric currently. Please make sure that the layer implements get_config and from_config when saving. In addition, please use the custom_objects arg when calling load_model()
在深入了解错误后,我开始了解如何传递 custom_objects。 然而,在阅读并尝试了一些东西之后,我仍然无法加载 model。有人可以告诉我正确的方法吗? 我的代码如下:
def get_metrics():
train_accuracy = tf.keras.metrics.CategoricalAccuracy(name="train_accuracy")
val_accuracy = tf.keras.metrics.CategoricalAccuracy(name="val_accuracy")
confusion_matrix = ConfusionMatrixMetric(20)
return confusion_matrix, train_accuracy, val_accuracy
def loss_fn(labels, logits):
epsilon = 1e-9
model_out = tf.nn.softmax(logits, axis=-1) + epsilon
ce = - (tf.math.log(model_out) * labels)
weight = labels * tf.math.pow(1 - model_out, gamma)
fl = alpha * weight * ce
loss = tf.reduce_max(fl, axis=-1)
return loss
def get_optimizer(steps_per_epoch, finetune=False):
lr = 0.001
if finetune:
lr = 0.00001
lr_fn = tf.keras.optimizers.schedules.PiecewiseConstantDecay(
[steps_per_epoch * 10], [lr, lr / 10], name=None
)
opt_op = tf.keras.optimizers.Adam(learning_rate=lr_fn)
return opt_op
class MyModel(keras.Model):
def compile(self, optimizer, loss_fn, metric_fn):
super(MyModel, self).compile()
self.optimizer = optimizer
self.loss_fn = loss_fn
self.confusion_matrix, self.train_accuracy, self.val_accuracy = metric_fn()
def train_step(self, train_data):
X, y = train_data
with tf.GradientTape() as tape:
logits = self(X, training=True)
loss = self.loss_fn(y, logits)
# Compute gradients
trainable_vars = self.trainable_variables
gradients = tape.gradient(loss, trainable_vars)
# Update weights
self.optimizer.apply_gradients(zip(gradients, trainable_vars))
# compute metrics keeping an moving average
y_pred = tf.nn.softmax(y, axis=-1)
self.train_accuracy.update_state(y, y_pred )
self.confusion_matrix.update_state(y, y_pred)
update_dict = {"train_accuracy": self.train_accuracy.result()}
if 'confusion_matrix_metric' in self.metrics_names:
self.metrics[0].add_results(update_dict)
return update_dict
class ConfusionMatrixMetric(tf.keras.metrics.Metric):
def __init__(self, num_classes, **kwargs):
super(ConfusionMatrixMetric, self).__init__(name='confusion_matrix_metric', **kwargs) # handles base args (e.g., dtype)
self.num_classes = num_classes
self.total_cm = self.add_weight("total", shape=(num_classes, num_classes), initializer="zeros")
def reset_states(self):
for s in self.variables:
s.assign(tf.zeros(shape=s.shape))
def update_state(self, y_true, y_pred, sample_weight=None):
self.total_cm.assign_add(self.confusion_matrix(y_true, y_pred))
return self.total_cm
def result(self):
return self.process_confusion_matrix()
def confusion_matrix(self, y_true, y_pred):
y_pred = tf.math.argmax(y_pred, 1)
cm = tf.math.confusion_matrix(y_true, y_pred, dtype=tf.float32, num_classes=self.num_classes)
return cm
def process_confusion_matrix(self):
cm = self.total_cm
diag_part = tf.linalg.diag_part(cm)
# accuracy = tf.math.reduce_sum(diag_part) / (tf.math.reduce_sum(cm) + tf.constant(1e-15))
precision = diag_part / (tf.math.reduce_sum(cm, 0) + tf.constant(1e-15))
recall = diag_part / (tf.math.reduce_sum(cm, 1) + tf.constant(1e-15))
f1 = 2 * precision * recall / (precision + recall + tf.constant(1e-15))
return f1
def add_results(self, output):
results = self.result()
for i in range(self.num_classes):
output['F1_{}'.format(i)] = results[i]
if __name__ == "__main__":
model_path = 'model/my_custom_model/'
create_folder(model_path)
callbacks = [tf.keras.callbacks.ModelCheckpoint(model_path)]
# train
model = MyModel(inputs, outputs)
model.summary()
opt_op = get_optimizer(100)
model.compile(optimizer=opt_op,
loss_fn=loss_fn,
metric_fn=get_metrics)
model.fit(train_data_gen(),
epochs=10,
callbacks=callbacks)
tf.keras.models.load_model(model_path)
抱歉代码太长。 但只是想确保我所做的一切都是正确且可以理解的。
正如您的错误说明,如果您想要子类化、使用和加载自定义指标,您应该实现get_config
方法。
你已经正确地构建了你的度量子类 class tf.Keras.metrics.Metric
,你只需要添加get_config
并用它获取你的参数(据我所知,你只有num_classes
):
def get_config(self):
base_config = super().get_config()
return {**base_config, "num_classes": self.num_classes}
此外,加载时,还必须加载自定义指标:
tf.keras.models.load_model(model_path, custom_objects={"ConfusionMatrixMetric": ConfusionMatrixMetric )
不过要注意以下几点( 摘自 Aurélien Géron 的《动手机器学习与 Scikit-Learn 和 TensorFlow》,第 2 版):
Keras API 目前只规定了如何使用子类化来定义层模型、回调和正则化器。 如果您构建其他组件(例如损失、指标、初始值设定项或约束)。 使用子类化,它们可能无法移植到其他 Keras 实现。 Keras API 很可能会更新以指定所有这些组件的子类化。
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