AlexNet Architecture PDF

**Introduction to the Architecture of Alexnet** Objective - When we talk about the Pre-trained model in the Computer Vision domain, Alexnet comes out as a leading architecture. - Let's understand the architecture of Alexnet as proposed by its authors. Introduction Alexnet won the Im...

**Introduction to the Architecture of Alexnet** Objective - When we talk about the Pre-trained model in the Computer Vision domain, Alexnet comes out as a leading architecture. - Let's understand the architecture of Alexnet as proposed by its authors. Introduction Alexnet won the Imagenet large-scale visual recognition challenge in 2012. The model was proposed in 2012 in the research paper named [Imagenet Classification with Deep Convolution Neural Network] by Alex Krizhevsky and his colleagues. *In this model, the depth of the network was increased in comparison to Lenet-5. In case you want to know more about Lenet-5, I will recommend you to check the following article-* - [[The Architecture of Lenet-5]](https://www.analyticsvidhya.com/blog/2021/03/the-architecture-of-lenet-5/) *Note: If you are more interested in learning concepts in an Audio-Visual format, We have this entire article explained in the video below. If not, you may continue reading.* The Alexnet has eight layers with learnable parameters. The model consists of five layers with a combination of max pooling followed by 3 fully connected layers and they use Relu activation in each of these layers except the output layer. They found out that using the relu as an activation function accelerated the speed of the training process by almost six times. They also used the dropout layers, that prevented their model from overfitting. Further, the model is trained on the Imagenet dataset. The Imagenet dataset has almost 14 million images across a thousand classes. In this article, you will get to know about the alex net and alexnet architecture also what is alexnet you will know so you will cover all about alexnet architecture in this article. Let's see the architectural details in this article. Table of contents Alexnet Architecture One thing to note here, since Alexnet is a deep architecture, the authors introduced padding to prevent the size of the feature maps from reducing drastically. The input to this model is the images of size 227X227X3. architecture of Alexnet layers Convolution and Maxpooling Layers Then we apply the first convolution layer with 96 filters of size 11X11 with stride 4. The activation function used in this layer is relu. The output feature map is 55X55X96. In case, you are unaware of how to calculate the output size of a convolution layer                           output= ((Input-filter size)/ stride)+1 Also, the number of filters becomes the channel in the output feature map. Next, we have the first Maxpooling layer, of size 3X3 and stride 2. Then we get the resulting feature map with the size 27X27X96. After this, we apply the second convolution operation. This time the filter size is reduced to 5X5 and we have 256 such filters. The stride is 1 and padding 2. The activation function used is again relu. Now the output size we get is 27X27X256. Again we applied a max-pooling layer of size 3X3 with stride 2. The resulting feature map is of shape 13X13X256. Now we apply the third convolution operation with 384 filters of size 3X3 stride 1 and also padding 1. Again the activation function used is relu. The output feature map is of shape 13X13X384. Then we have the fourth convolution operation with 384 filters of size 3X3. The stride along with the padding is 1. On top of that activation function used is relu. Now the output size remains unchanged i.e 13X13X384. After this, we have the final convolution layer of size  3X3 with 256 such filters. The stride and padding are set to one also the activation function is relu. The resulting feature map is of shape 13X13X256. So if you look at the architecture till now, the number of filters is increasing as we are going deeper. Hence it is extracting more features as we move deeper into the architecture. Also, the filter size is reducing, which means the initial filter was larger and as we go ahead the filter size is decreasing, resulting in a decrease in the feature map shape. Next, we apply the third max-pooling layer of size 3X3 and stride 2. Resulting in the feature map of the shape 6X6X256. Fully Connected and Dropout Layers  After this, we have our first dropout layer. The drop-out rate is set to be 0.5. Then we have the first fully connected layer with a relu activation function. The size of the output is 4096. Next comes another dropout layer with the dropout rate fixed at 0.5. This followed by a second fully connected layer with 4096 neurons and relu activation. Finally, we have the last fully connected layer or output layer with 1000 neurons as we have 10000 classes in the data set. The activation function used at this layer is Softmax. This is the architecture of the Alexnet model. It has a total of 62.3 million learnable parameters. Why is AlexNet so important? AlexNet is Important explain in [[these steps]](https://github.com/amir-saniyan/AlexNet): **Breakthrough Performance:** Achieved a significant improvement in image classification accuracy in 2012, showcasing the power of machine learning algorithms. **Deep Architecture:** Utilized a deep network with eight layers, much deeper than previous models, contributing to advancements in CNN architectures. **Use of GPUs:** Leveraged GPUs to speed up training, significantly enhancing performance and efficiency in processing large datasets. **Innovative Techniques:** - **ReLU Activation:** Employed Rectified Linear Units for faster training, an essential component in the optimization of gradient-based learning. - **Dropout:** Prevented overfitting by randomly dropping neurons during training, improving model robustness. - **Data Augmentation:** Enhanced model generalization through techniques like image translations and reflections, crucial for effective data preprocessing. **Large-Scale Data:** Trained on the large ImageNet dataset, which contains millions of images, demonstrating the importance of extensive and diverse datasets in machine learning. **Inspiration for Research:** This work paved the way for more advanced neural network architectures and deep learning research, influencing subsequent innovations in the field. What is the difference between AlexNet and ResNet? AlexNet and ResNet are both convolutional neural networks (CNNs) that played a major role in the advancement of computer vision. Here's the key differences of these pretrained models: AlexNet: Introduced in 2012, AlexNet, developed by Geoffrey Hinton's team, has a relatively shallow architecture with stacked convolutional and pooling layers. Despite its groundbreaking nature at the time, this depth limitation affects its ability to learn complex features. It utilizes techniques such as normalization and the sigmoid activation function for classification tasks. ResNet: Introduced in 2015, ResNet builds upon AlexNet by using a much deeper architecture with "skip connections." These connections allow the network to learn from the gradients of previous layers, alleviating the vanishing gradient problem that hinders training in very deep networks. This enables ResNet to achieve significantly higher accuracy. ResNet also excels in tasks such as image segmentation and classification due to its robust architecture. End Notes To quickly summarize the architecture that we have seen in this article. - It has 8 layers with learnable parameters. - The input to the Model is RGB images. - It has 5 convolution layers with a combination of max-pooling layers. - Then it has 3 fully connected layers. - The activation function used in all layers is Relu. - It used two Dropout layers. - The activation function used in the output layer is Softmax. - The total number of parameters in this architecture is 62.3 million. In this article, we learn about the Alexnet architecture its state of the art different regularization i.e tanh , validation different classifier their error i.e top 5 error like CPU, pixels So We are Hoping you like the article and Whatever We covered on related to the alexnet or on these topics alexnet CNN, alexnet architecture in deep learning and also you knew Now what is alexnet and alexnet cnn. **Q1. What is the use of AlexNet?** A. AlexNet is a pioneering convolutional neural network (CNN) used primarily for image recognition and classification tasks. It won the ImageNet Large Scale Visual Recognition Challenge in 2012, marking a breakthrough in deep learning. AlexNet's architecture, with its innovative use of convolutional layers and rectified linear units (ReLU), laid the foundation for modern deep learning models, advancing computer vision and pattern recognition applications. **Q2. Why AlexNet is better than CNN?** A. AlexNet is a specific type of CNN, which is a kind of neural network particularly good at understanding images. When AlexNet was introduced, it showed impressive results in recognizing objects in pictures. It became popular because it was deeper (had more layers) and used some smart tricks to improve accuracy. So, AlexNet is not better than CNN; it is a type of CNN that was influential in making CNNs popular for image-related tasks. **Q3. What are the advantages of AlexNet?** **Deep architecture:** Learns complex features.\ **ReLU activation:** Faster training, avoids vanishing gradient.\ **Overlapping pooling:** Improves accuracy.\ **Data augmentation:** Prevents overfitting.\ **GPU acceleration:** Faster training.\ **State-of-the-art accuracy:** Best performance at its time.\ **Pioneered deep learning:** Inspired future research. **Q4.What is AlexNet architecture in CNN?** 8 layers: 5 conv, 3 pooling, 2 FC, 1 softmax\ ReLU activation, overlapping pooling, data aug\ GPU acceleration\ Pioneering CNN **Q5. What are the properties of AlexNet?** AlexNet is a deep CNN with 8 layers, using ReLU, overlapping pooling, LRN, dropout, and data augmentation. It achieved a top-5 error rate of 15.7% on ImageNet in 2012, significantly outperforming previous methods. 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