Convolutions, pooling, padding, stride, classic architectures, transfer learning, object detection and segmentation.
40 cards · basic cards · AI-written, checked twice. Edit anything.
- What is a convolution operation in a CNN?
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A mathematical operation where a small matrix (kernel/filter) slides across an input and computes element-wise products summed to produce output feature maps.
- What is a kernel (or filter) in CNNs?
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A small learnable matrix that slides over the input to detect local features like edges, textures, or patterns.
- What does stride control in a convolution?
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The step size by which the kernel moves across the input; larger stride reduces output spatial dimensions.
- Why use padding in convolutions?
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To preserve spatial dimensions at image edges, prevent information loss at borders, and allow kernels to process edge pixels.
- What is the difference between valid and same padding?
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Valid padding applies no padding and output shrinks; same padding adds zeros so output matches input spatial dimensions.
- How do you calculate the output size after a convolution?
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Formula: (Input size - Kernel size + 2*Padding) / Stride + 1
- What is the receptive field in CNNs?
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The region of the input that influences one output neuron; it grows exponentially as layers stack through convolution and pooling.
- What are 1x1 convolutions used for?
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Dimensionality reduction of channels, feature mixing, and adding nonlinearity while reducing computation; common in bottleneck layers.
- What is max pooling?
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A downsampling operation that selects the maximum value in a local window, reducing spatial dimensions while preserving dominant features.
- What is average pooling?
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A downsampling operation that computes the mean of values in a local window; produces smoother output than max pooling.
- Why use pooling in CNNs?
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To reduce computational complexity and parameters, achieve translation invariance, and provide implicit regularization against overfitting.
- What is the key difference between max and average pooling?
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Max pooling selects the peak value in each window (preserves strongest features), while average pooling computes the mean (smoother representation).
- What is LeNet-5?
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An early CNN architecture designed by Yann LeCun for digit recognition; pioneered convolutional and pooling concepts with 7 layers.
- What is AlexNet?
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A deep CNN that won ImageNet 2012; pioneered ReLU activation, dropout regularization, and successful GPU training of deep networks.
- What are the key characteristics of VGGNet?
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Uses stacked small 3x3 filters in depth rather than large filters; demonstrates that network depth is more important than filter size.