Generative Adversarial network

Generative Adversarial Networks or GANs are a deep learning-based generative model that is used for unsupervised learning.

What are GANs or Generative Adversarial Networks?

It is essentially a system wherever 2 competitor neural networks compete with one another to form or generate variations within the data. It first described in a paper in 2014 by Ian Ian Goodfellow, et al., and a standardized and much stable model theory was proposed by Alec Radford in 2016 which also known as DGCAN also known as DCGAN or we can moreover call it as (Deep Convolutional Generative Adversarial Networks).

Most of the GANs today use Deep C onvolutional Generative Adversarial Networks

. The GANs
the architecture consists of two sub-models known as the “generator model” and the “discriminative model”.

A generator network takes a sample and generates a sample of data. A discriminator network decides whether the data generated or taken from the real sample using a binary classification problem with the help of a sigmoid function that gives the output in the form of the range 0 & 1.

Generative Adversely Networks
Generative Adversely Networks

What are generative models?

Generative models are nothing but those models that use an associate degree neglected learning approach. In a generative model, there are samples in the data i.e. input variables X, but it lacks the
output variable Y and we use the only input variables to train the generative model
. It recognizes patterns from the input variables to generate an output that is unknown and based on the training data only.

supervised and unsupervised

In supervised learning, we are more aligned towards creating predictive models from the input variables. This type of modeling also known as “discriminative modeling”. A classification drawback the model needs to discriminate on which class the example belongs to. On the other hand, unsupervised models used to create or generate new examples in the input distribution.

To define a generative model in layman terms, we can say generative models are able to generate new examples from the sample that are not only similar to the examples but are indistinguishable as well. The most common example of a generative model is a bias classifier which is more of a used other discriminative model. Other examples of generative models include the Gaussian mixture model and a rather modern example that is generative adverse networks.

How GANs work?

Generative means that the model follows the unsupervised learning approach and is a generative model. In Adversarial the model trained in an adversarial setting. Network merely suggests that for the coaching of the model we use the neural networks as artificial intelligence algorithms. In GANs there is a generator network that takes a sample and generates a sample of data. After this, the discriminator network decides whether or not the info generated or taken from the real sample employing a binary classification drawback with the assistance of a sigmoid functionthat provides the output in the range 0 to 1.

The generative model analyzes the distribution of the data in such a way that after the training phase the
probability of the discriminator making a mistake maximizes. The discriminator on the opposite hand predicated on a model that may estimate the probability that the sample is coming from the real data or not the generator.

How to train a GAN?

Generative Adversarial Network trained in two phases.
It is the phase where we train the discriminator and we actually freeze the generator. This means that the training set for the generator turned false and the network will only do the forward pass and they will not be any backpropagation.

Basically, the discriminator trained with real data and checks if it can predict them accurately. The same with the fake data to identify them as fake. After this, there is the second part where we train the generator and freeze the discriminator. So we get the result from the first phase and we use them to make better from the previous state to try and fool the discriminator better.

To understand this in the layman term

step 1
Define the problem and collect the data.
step 2
Choose the architecture of GAN. Depending on your problem you have to choose how your
GAN should look like.
step 3
Training the discriminator on real data. We train the discriminator with real data to predict them as real for n number of times.
step 4
We generate the fake inputs from the generator. In this step, we are going to generate the fake samples from the generator

step 5

We train the discriminator on fake data. So whatever samples generated from the generator network going to train the discriminator to predict the generated data as fake. That’s how we know that the discriminator is actually predicting the values correctly.

step 6

Train the generated with the output of the discriminator. So after getting the discriminator predictions we train the generator to fool the discriminator. That’s how we train the GAN to actually get our solution to the problem.

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Challenges faced by Generative Adversarial Networks?

The concept of GANs is rather fascinating, but there are a lot of drawbacks that can cause a lot of
obstacles in its path. Some of the major challenges faced by GANs are

  1. stability
    There should be a stability between the discriminator and also the generator network otherwise the full network would simply fall.
    For example
    In case the discriminator is too powerful the generator will fail to train altogether. It will not be able to push
    fake samples to the discriminator and it will always identify them as fake. If the
    discriminator network is too lenient, so any image that would be generated by the generator network would make the network useless.
stability between the discriminator and also the generator network
stability between the discriminator and also the generator network

2. positioning of the objects
GANs fail miserably in deciding the positioning of the objects in terms of how many times the object should occur at that location. Suppose we have an image in which three dogs with two eyes and sometimes GAN will fail to determine the positioning of the objects. Sometimes it will generate an image with “one dog and six eyes”.

3. 3D perspective troubles
GANs not able to understand the perspective. It will often give a flat image for a 3D object.

4. understanding the global objects
GANs have a problem of understanding the global objects. It cannot differentiate or understand a holistic structure like flowers and trees. Newer types of GANs more advanced than (Deep Convolutional Generative Adversarial Networks) and are expected to overcome these shortcomings altogether.

Generative Adversarial Network Applications

1.prediction of next frame in a video

The prediction of future events in a video frame is made possible with the help of GANs and DVD GAN( Dual Video Discriminative GAN) can generate 256 by 256 videos of notable fidelity up to 48 frames in length. This used for various purposes including surveillance, in which we can determine the activities in a frame that gets distorted due to other factors like rain, dust, fog, etc.

2.The text to image generation
Basically, object-driven attentive GAN which also known as “Object GAN” performs the text-to-image synthesis in two steps. Generating the semantic layout and then generating the image by synthesizing the image by using a deconvolutional image generator is the final step.
This can be used intensively to generate images by understanding the captions, the layouts and refine details by synthesizing the words.

text to image
text to image

3.image to image translation
Pics topics is a model that is designed for the general-purpose image to image translation.

4.Enhancing the resolution of an image

Super-Resolution Generative Adversarial Network
or also known as SR GAN.
It can generate super-resolution images from low-resolution images with finer details and better quality. Imagine a higher quality image with finer details generated from a low-resolution image the amount of help it would produce to identify details in lower resolution images may be used for wider purposes including surveillance, documentation, security, detecting patterns and etc

5.Interactive image generation

GANs used to generate interactive images. Computer Science and Artificial intelligence
library are
also known as CSAIL has developed a GAN that can generate 3d models with realistic lighting and reflections enabled by shape and texture editing. Recently researchers have come up with a model that can synthesize a re-enacted face animated by a person’s movement while preserving the appearance of the face at the same time.

By Pravin

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