Apply GANs week2

Image-to-Image Translation

What is paired translation?
When you have corresponding input-output images that you can gather training data for.

Correct! Paired translation means that you have input-output pairs that map exactly onto each other (1-to-1).

PatchGAN

What is the output of the Pix2Pix discriminator (PatchGAN)?
A matrix with values between 0 and 1 indicating realness.

Pix2Pix: U-Net

1. Pix2Pix先用U-net来做image segmentation, 再用U-net和segmentation后的image来做generate.

2. Skip connection可以改善back propagation的性能，在propagation中也可以提供encode时损失的信息

3. 在decoder前几个block中用了dropout，来使block在不同的Iteration中学到不同的东西, inference和test时关掉dropout(但要do scale by probability)

What is the purpose of the skip connections in the Pix2Pix generator?
They allow information to flow to later layers by reducing the vanishing gradient problem, which occurs when there are too many layers.

Correct! Skip connections help prevent the vanishing gradient problem when gradients get too small when there are many layers because they
are weighed less and less as the layers get deeper.

Pix2Pix: Pixel Distance Loss Term

Why is pixel distance used for L1 regularization in Pix2Pix?
Because the real output image and the generated image should be encouraged to be similar.

Correct! Since they are so correlated, you can use the absolute difference or pixel difference.

Put together