<分区>
我正在使用形状为 (400,22) 的二维张量作为输入和输出来训练 CNN 模型。我将 categorical_crossentropy 用作损失和指标。然而，损失/指标值非常不同。
我的模型有点像这样:
<强>1。使用样本权重，并在 model.compile 中使用 metrics= 传递指标。
# Imports
import tensorflow as tf
from tensorflow.keras.layers import *
from tensorflow.keras.optimizers import *
from tensorflow.keras.regularizers import *
from tensorflow.keras import *
import numpy as np
# Build the model
X_input = Input(shape=(400,22))
X = Conv1D(filters=32, kernel_size=2, activation='elu',
kernel_regularizer=L2(1e-4), bias_regularizer=L2(1e-4),
padding='same')(X_input)
X = Dropout(0.2)(X)
X = Conv1D(filters=32, kernel_size=2, activation='elu',
kernel_regularizer=L2(1e-4), bias_regularizer=L2(1e-4),
padding='same')(X)
X = Dropout(0.2)(X)
y = Conv1D(filters=22, kernel_size=1, activation='softmax',
kernel_regularizer=L2(1e-4), bias_regularizer=L2(1e-4),
padding='same')(X)
model = Model(X_input, y, name='mymodel')
# Compile and train the model (with metrics=[])
model.compile(optimizer=Adam(1e-3),
loss=tf.keras.losses.categorical_crossentropy,
metrics=[tf.keras.losses.categorical_crossentropy])
Xtrain = np.random.rand(20,400,22)
ytrain = np.random.rand(20,400,22)
np.random.seed(0)
sample_weight = np.random.choice([0.01, 0.1, 1], size=20)
history = model.fit(x=Xtrain, y=ytrain, sample_weight=sample_weight, epochs=4)
Epoch 1/4
1/1 [==============================] - 0s 824us/step - loss: 10.2952 - categorical_crossentropy: 34.9296
Epoch 2/4
1/1 [==============================] - 0s 785us/step - loss: 10.2538 - categorical_crossentropy: 34.7858
Epoch 3/4
1/1 [==============================] - 0s 772us/step - loss: 10.2181 - categorical_crossentropy: 34.6719
Epoch 4/4
1/1 [==============================] - 0s 766us/step - loss: 10.1903 - categorical_crossentropy: 34.5797
从结果可以看出，Keras 在计算指标时没有使用样本权重，因此它大于损失。如果我们将样本权重更改为 ones，我们将得到以下结果:
<强>2。样本权重 = ones，在 `model.compile.
中使用metrics= 传递指标
# Compile and train the model
model.compile(optimizer=Adam(1e-3),
loss=tf.keras.losses.categorical_crossentropy,
metrics=[tf.keras.losses.categorical_crossentropy])
Xtrain = np.random.rand(20,400,22)
ytrain = np.random.rand(20,400,22)
np.random.seed(0)
sample_weight = np.ones((20,))
history = model.fit(x=Xtrain, y=ytrain, sample_weight=sample_weight, epochs=4)
Epoch 1/4
1/1 [==============================] - 0s 789us/step - loss: 35.2659 - categorical_crossentropy: 35.2573
Epoch 2/4
1/1 [==============================] - 0s 792us/step - loss: 35.0647 - categorical_crossentropy: 35.0562
Epoch 3/4
1/1 [==============================] - 0s 778us/step - loss: 34.9301 - categorical_crossentropy: 34.9216
Epoch 4/4
1/1 [==============================] - 0s 736us/step - loss: 34.8076 - categorical_crossentropy: 34.7991
现在指标和损失与 ones 的样本权重非常接近。据我所知，由于丢失、正则化的影响以及指标是在每个时期结束时计算的事实，损失略大于指标，而损失是训练中各批处理的平均值。
如何获取包含样本权重的指标？
<强>3。更新:使用样本权重，并在 model.compile 中使用 weighted_metrics= 传递指标。
有人建议我在 model.compile 中使用 weighted_metrics=[...] 而不是 metrics=[...] .然而，Keras 仍然没有将样本权重纳入指标的评估。
# Compile and train the model
model.compile(optimizer=Adam(1e-3),
loss=tf.keras.losses.categorical_crossentropy,
weighted_metrics=[tf.keras.losses.categorical_crossentropy])
Xtrain = np.random.rand(20,400,22)
ytrain = np.random.rand(20,400,22)
np.random.seed(0)
sample_weight = np.random.choice([0.01, 0.1, 1], size=20)
history = model.fit(x=Xtrain, y=ytrain, sample_weight=sample_weight, epochs=4)
Epoch 1/4
1/1 [==============================] - 0s 764us/step - loss: 10.2581 - categorical_crossentropy: 34.9224
Epoch 2/4
1/1 [==============================] - 0s 739us/step - loss: 10.2251 - categorical_crossentropy: 34.8100
Epoch 3/4
1/1 [==============================] - 0s 755us/step - loss: 10.1854 - categorical_crossentropy: 34.6747
Epoch 4/4
1/1 [==============================] - 0s 746us/step - loss: 10.1631 - categorical_crossentropy: 34.5990
如何确保样本权重在指标中得到评估？