La gradient de rétropropagation est un algorithme fondamental utilisé dans l'entraînement des réseaux neuronaux artificiels. réseaux neuronaux. It is part of the backpropagation process, which involves calculating the gradient of the fonction de perte with respect to each weight by the règle de la chaîne, propagating the error backwards through the network. This method is essential for updating the weights in the network, allowing it to learn from the données d'entraînement.
Le processus commence par effectuer une passage en avant through the network, where an input is fed through the layers to obtain an output. The output is then compared to the actual target value to compute the loss, or error, using a defined loss function. The backpropagation algorithm then calculates the gradient of this loss with respect to each weight in the network.
To compute the gradients, backpropagation starts from the output layer and moves backwards to the input layer. For each layer, it computes the gradient of the loss concerning the weights, using the local gradients of the fonctions d'activation applied at each layer. This is where activation functions come into play, as they determine how the output of each neuron is calculated from its inputs.
Once the gradients are computed, they are used to update the weights in the direction that reduces the loss, typically using an algorithme d'optimisation like Stochastic Gradient Descent (SGD). The magnitude of the update is controlled by a hyperparameter known as the learning rate. Through iterative training, the neural network adjusts its weights to minimize the error, improving its predictions on unseen data.
In summary, Backpropagation Gradient plays a crucial role in the training of neural networks, enabling them to learn complex apprendre des motifs à partir des données en réduisant systématiquement l'erreur de prédiction.