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[英]TensorFlow 2.0 SparseCategoricalCrossentropy valueError: Shape mismatch: The shape of labels should equal the shape of logits except for the last
[英]SparseCategoricalCrossentropy Shape Mismatch
我想對 SparseCategoricalCrossentropy 函數做一個簡單的測試,看看它到底對輸出做了什么。 為此,我使用 MobileNetV2 的最后一層的輸出。
import keras.backend as K
full_model = tf.keras.applications.MobileNetV2(
input_shape=(224,224,3),
alpha=1.0,
include_top=True,
weights="imagenet",
input_tensor=None,
pooling=None,
classes=1000,
classifier_activation="softmax",)
func = K.function(full_model.layers[1].input, full_model.layers[155].output)
conv_output = func([processed_image])
y_pred = np.single(conv_output)
y_true = np.zeros(1000).reshape(1,1000)
y_true[0][282] = 1
scce = tf.keras.losses.SparseCategoricalCrossentropy()
scce(y_true, y_pred).numpy()
processed_image
是先前創建的1x224x224x3陣列。
我收到錯誤ValueError: Shape mismatch: The shape of labels (received (1000,)) should equal the shape of logits except for the last dimension (received (1, 1000)).
我嘗試重塑數組以匹配提到的錯誤的維度,但它似乎不起作用。 它接受什么形狀?
由於您使用的是SparseCategoricalCrossentropy
損失函數,因此y_true
的形狀應為[batch_size]
,而y_pred
的形狀應為[batch_size, num_classes]
。 此外, y_true
應該由整數值組成。 請參閱文檔。 在你的具體例子中,你可以嘗試這樣的事情:
import keras.backend as K
import tensorflow as tf
import numpy as np
full_model = tf.keras.applications.MobileNetV2(
input_shape=(224,224,3),
alpha=1.0,
include_top=True,
weights="imagenet",
input_tensor=None,
pooling=None,
classes=1000,
classifier_activation="softmax",)
batch_size = 1
processed_image = tf.random.uniform(shape=[batch_size,224,224,3])
func = K.function(full_model.layers[1].input,
full_model.layers[155].output)
conv_output = func([processed_image])
y_pred = np.single(conv_output)
# Generates an integer between 0 and 999 representing a class index.
y_true = np.random.randint(low = 0, high = 999, size = batch_size)
# [984]
scce = tf.keras.losses.SparseCategoricalCrossentropy()
scce(y_true, y_pred).numpy()
# y_pred encodes a probability distribution here and the calculated loss is 10.69202
您可以嘗試使用batch_size
來查看一切是如何工作的。 在上面的例子中,我只使用了 1 的batch_size
。
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