tf.assign_add()

本文介绍了TensorFlow中tf.assign_add()函数的用法,通过一个简单的示例展示了如何使用该函数来更新变量值。首先创建了一个名为x的Variable实例,然后使用tf.assign_add()将x的值增加2,并在Session中运行初始化操作后打印结果。

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tf.assign_add()将ref加上value,必须要初始化
参数:

tf.assign_add(
    ref,
    value,
    use_locking=None,
    name=None
)

使用案例:

import tensorflow as tf

x = tf.Variable(1)
y = tf.assign_add(x, 2)
sess = tf.Session()
sess.run(tf.global_variables_initializer())
print(sess.run(y))
``` !mkdir -p ~/.keras/datasets !cp work/mnist.npz ~/.keras/datasets/ import warnings warnings.filterwarnings("ignore") from keras.datasets import mnist (train_images, train_labels), (test_images, test_labels) = mnist.load_data() print(f"训练数据形状: {train_images.shape}") print(f"训练标签长度: {len(train_labels)}") print(f"测试数据形状: {test_images.shape}") print(f"测试标签长度: {len(test_labels)}") from keras import models from keras import layers # 构建神经网络模型 network = models.Sequential() network.add(layers.Dense(512, activation='relu', input_shape=(28 * 28,))) # 隐藏层:512个神经元,激活函数为ReLU network.add(layers.Dense(10, activation='softmax')) # 输出层:10个分类,激活函数为Softmax # 编译模型 network.compile(optimizer='rmsprop', loss='categorical_crossentropy', metrics=['accuracy']) # 数据预处理 train_images = train_images.reshape((60000, 28 * 28)) # 将图像展平成一维向量 train_images = train_images.astype('float32') / 255 # 归一化到[0,1] test_images = test_images.reshape((10000, 28 * 28)) test_images = test_images.astype('float32') / 255 # 标签编码 from keras.utils import to_categorical train_labels = to_categorical(train_labels) test_labels = to_categorical(test_labels) # 训练模型 network.fit(train_images, train_labels, epochs=5, batch_size=128) # 测试模型性能 test_loss, test_acc = network.evaluate(test_images, test_labels) print('Test accuracy:', test_acc)```W0402 08:09:22.415642 140410418362176 deprecation.py:323] From /opt/conda/lib/python3.6/site-packages/tensorflow_core/python/ops/math_grad.py:1424: where (from tensorflow.python.ops.array_ops) is deprecated and will be removed in a future version. Instructions for updating: Use tf.where in 2.0, which has the same broadcast rule as np.where W0402 08:09:22.484165 140410418362176 module_wrapper.py:139] From /opt/conda/lib/python3.6/site-packages/keras/backend/tensorflow_backend.py:986: The name tf.assign_add is deprecated. Please use tf.compat.v1.assign_add instead. W0402 08:09:22.495126 140410418362176 module_wrapper.py:139] From /opt/conda/lib/python3.6/site-packages/keras/backend/tensorflow_backend.py:973: The name tf.assign is deprecated. Please use tf.compat.v1.assign instead. W0402 08:09:22.537523 140410418362176 module_wrapper.py:139] From /opt/conda/lib/python3.6/site-packages/keras/backend/tensorflow_backend.py:2741: The name tf.Session is deprecated. Please use tf.compat.v1.Session instead. W0402 08:09:22.546429 140410418362176 module_wrapper.py:139] From /opt/conda/lib/python3.6/site-packages/keras/backend/tensorflow_backend.py:174: The name tf.get_default_session is deprecated. Please use tf.compat.v1.get_default_session instead. W0402 08:09:22.548026 140410418362176 module_wrapper.py:139] From /opt/conda/lib/python3.6/site-packages/keras/backend/tensorflow_backend.py:181: The name tf.ConfigProto is deprecated. Please use tf.compat.v1.ConfigProto instead. W0402 08:09:22.566734 140410418362176 module_wrapper.py:139] From /opt/conda/lib/python3.6/site-packages/keras/backend/tensorflow_backend.py:190: The name tf.global_variables is deprecated. Please use tf.compat.v1.global_variables instead. W0402 08:09:22.567799 140410418362176 module_wrapper.py:139] From /opt/conda/lib/python3.6/site-packages/keras/backend/tensorflow_backend.py:199: The name tf.is_variable_initialized is deprecated. Please use tf.compat.v1.is_variable_initialized instead. W0402 08:09:22.613820 140410418362176 module_wrapper.py:139] From /opt/conda/lib/python3.6/site-packages/keras/backend/tensorflow_backend.py:206: The name tf.variables_initializer is deprecated. Please use tf.compat.v1.variables_initializer instead.
04-03
class ClassSpecificPrecision(tf.keras.metrics.Metric): def __init__(self, class_id, num_classes=8, name="class_precision", **kwargs): """ 为指定类别计算精确率 参数: class_id: 要计算精确率的类别ID (0-7) num_classes: 总类别数 (默认为8) name: 指标名称 """ super().__init__(name=name, **kwargs) self.class_id = class_id self.num_classes = num_classes # 初始化真正例(TP)和预测正例(PP)计数器 self.true_positives = self.add_weight( name="tp", initializer="zeros", dtype=tf.float32) self.predicted_positives = self.add_weight( name="pp", initializer="zeros", dtype=tf.float32) def update_state(self, y_true, y_pred, sample_weight=None): # 将标签转换为整数类型 y_true = tf.cast(y_true, tf.int32) # 获取预测类别 (形状: [batch_size]) y_pred_class = tf.argmax(y_pred, axis=-1, output_type=tf.int32) # 计算真正例 (TP): 实际为class_id且预测为class_id true_positive = tf.logical_and( tf.equal(y_true, self.class_id), tf.equal(y_pred_class, self.class_id) ) # 计算预测正例 (PP): 预测为class_id (不论实际类别) predicted_positive = tf.equal(y_pred_class, self.class_id) # 应用样本权重 (如果提供) if sample_weight is not None: true_positive = tf.cast(true_positive, tf.float32) * sample_weight predicted_positive = tf.cast(predicted_positive, tf.float32) * sample_weight else: true_positive = tf.cast(true_positive, tf.float32) predicted_positive = tf.cast(predicted_positive, tf.float32) # 更新状态变量 self.true_positives.assign_add(tf.reduce_sum(true_positive)) self.predicted_positives.assign_add(tf.reduce_sum(predicted_positive)) def result(self): # 避免除以零错误 return tf.where( self.predicted_positives > 0, self.true_positives / self.predicted_positives, 0.0 ) def reset_state(self): # 重置计数器 self.true_positives.assign(0.0) self.predicted_positives.assign(0.0) 上面自定义的指标输出为什么会超过100.0
最新发布
07-26
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