Implementation of CycleGAN : Unpaired Image-to-Image Translation using Cycle-Consistent Adversarial Networks using pytorch. Futhermore, this implementation is using multitask learning with semi-supervised leaning which means utilize labels of data. This model converts male to female or female to male. Following image shows improvements such as facial features(make-up, mustache, beard, etc) and image qualities.

original : without semi-supervised learning / improved : with semi-supervised learning

1. Batch size 1 -> 16
2. Instance Normalization -> Batch Normalization
3. Model architecture
4. Smooth labeling
5. Multitask learning with classification loss (semi-supervised learning).

1. Increasing Batch Size & Replacing Instance Norm with Batch Norm
This change makes the model recognize the difference of hair length between male and female. The generator started to draw or erase hair after applying this change.

2. Smooth Labeling & Model Architecture Change
Basicially, the discriminator easily overwhelms the generator. If it happens, the generator tries to fool the discriminator in an improper way. The balance between discriminator and generator is important for the performance. To solve this problem, smooth labeling is used and model architecture is changed.

3. No Batch Norm in the First Convolution in Discriminator
DCGAN suggests not to use normalization in the first convolution. If you don't follow this, the generator will make images with range of approximately -0.7 ~ 0.7 instead of -1.0 ~ 1.0, the blurry images.

4. Semi-Supervised Learning with Classification Loss
Discriminators need to classify domains not only measure the realism. The weight of classification loss, cls_lambda is 1 for training the discriminators and 0.1 for training generators to encourage the generators to focus more on the realism. The Followings are effects of this change.

• The image quality and clearity increase in most cases.
• The model recognizes the features of each gender such as mustache, beard, color lens and make-up better
• However, recognition of hair length becomes worse.

• Python 3.5+
• PyTorch 0.2.0

CelebA dataset is used. After downloading the dataset, all images are supposed to be located in the following path.

• data/train/0 : Training male images
• data/train/1 : Training female images
• data/val/0 : Validation male images
• data/val/1 : Validation female images
• data/test/0 : Test male images
• data/test/1 : Test female images