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Why Gaussian latent variable (noise) for GAN?


Can the Generative Adversarial Network useful for Outlier detection and Outlier explanation in a high dimentional numerical data?Strange patterns from GANWhy should I normalize also the output data?Generative adversarial networks for multiple distribution noise removalHow can I train Generative Adversarial Inverse Reinforcement Learning(GAIL) by feeding encoded state representations in the GAN architecture ?Architecture Advice for training a GANWhat mu and sigma vector really mean in VAE?EGAN Paper With Confusing NotationWhy do most GAN (Generative Adversarial Network) implementations have symmetric discriminator and generator architectures?What is the interpretation of the expectation notation in the GAN formulation?













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When I was reading about GAN, the thing I don't understand is why people often choose the input to a GAN (z) to be samples from a Gaussian? - and then are there also potential problems associated with this?










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    5












    $begingroup$


    When I was reading about GAN, the thing I don't understand is why people often choose the input to a GAN (z) to be samples from a Gaussian? - and then are there also potential problems associated with this?










    share|improve this question









    New contributor




    asahi kibou is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
    Check out our Code of Conduct.







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      $begingroup$


      When I was reading about GAN, the thing I don't understand is why people often choose the input to a GAN (z) to be samples from a Gaussian? - and then are there also potential problems associated with this?










      share|improve this question









      New contributor




      asahi kibou is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.







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      When I was reading about GAN, the thing I don't understand is why people often choose the input to a GAN (z) to be samples from a Gaussian? - and then are there also potential problems associated with this?







      deep-learning gan gaussian






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      edited 2 days ago









      Esmailian

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      asked Mar 16 at 22:27









      asahi kibouasahi kibou

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          $begingroup$


          Why people often choose the input to a GAN (z)
          to be samples from a Gaussian?




          Generally, for two reasons: (1) mathematical simplicity, (2) working well enough in practice. However, as we explain, under additional assumptions the choice of Gaussian could be more justified.



          Compare to uniform distribution. Gaussian distribution is not as simple as uniform distribution but it is not that far off either. It adds "concentration around the mean" assumption to uniformity, which gives us the benefits of parameter regularization in practical problems.



          The least known. Use of Gaussian is best justified for continuous quantities that are the least known to us, e.g. noise $epsilon$ or latent factor $z$. "The least known" could be formalized as "distribution that maximizes entropy for a given variance". The answer to this optimization is $N(mu, sigma^2)$ for arbitrary mean $mu$. Therefore, in this sense, if we assume that a quantity is the least known to us, the best choice is Gaussian. Of course, if we acquire more knowledge about that quantity, we can do better than "the least known" assumption, as will be illustrated in the following examples.



          This would be the answer to "why we assume a Gaussian noise in probabilistic regression or Kalman filter?" too.




          Are there also potential problems associated with this?




          Yes. When we assume Gaussian, we are simplifying. If our simplification is unjustified, our model will under-perform. At this point, we should search for an alternative assumption. In practice, when we make a new assumption about the least known quantity (based on acquired knowledge or speculation), we could extract that assumption and introduce a new Gaussian one, instead of changing the Gaussian assumption. Here are two examples:



          1. Example in regression (noise). Suppose we have no knowledge about observation $A$ (the least known), thus we assume $A sim N(mu, sigma^2)$. After fitting the model, we may observe that the estimated variance $hatsigma^2$ is high. After some investigation, we may assume that $A$ is a linear function of measurement $B$, thus we extract this assumption as $A = colorblueb_1B +c + epsilon_1$, where $epsilon_1 sim N(0, sigma_1^2)$ is the new "the least known". Later, we may find out that our linearity assumption is also weak since, after fitting the model, the observed $hatepsilon_1 = A - hatb_1B -hatc$ also has a high $hatsigma_1^2$. Then, we may extract a new assumption as $A = b_1B + colorblueb_2B^2 + c + epsilon_2$, where $epsilon_2 sim N(0, sigma_2^2)$ is the new "the least known", and so on.


          2. Example in GAN (latent factor). Upon seeing unrealistic outputs from GAN (knowledge) we may add $colorbluetextmore layers$ between $z$ and the output (extract assumption), in the hope that the new network (or function) with the new $z_2 sim N(0, sigma_2^2)$ would lead to more realistic outputs, and so on.






          share|improve this answer











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            0












            $begingroup$


            Why people often choose the input to a GAN (z)
            to be samples from a Gaussian?




            Generally, for two reasons: (1) mathematical simplicity, (2) working well enough in practice. However, as we explain, under additional assumptions the choice of Gaussian could be more justified.



            Compare to uniform distribution. Gaussian distribution is not as simple as uniform distribution but it is not that far off either. It adds "concentration around the mean" assumption to uniformity, which gives us the benefits of parameter regularization in practical problems.



            The least known. Use of Gaussian is best justified for continuous quantities that are the least known to us, e.g. noise $epsilon$ or latent factor $z$. "The least known" could be formalized as "distribution that maximizes entropy for a given variance". The answer to this optimization is $N(mu, sigma^2)$ for arbitrary mean $mu$. Therefore, in this sense, if we assume that a quantity is the least known to us, the best choice is Gaussian. Of course, if we acquire more knowledge about that quantity, we can do better than "the least known" assumption, as will be illustrated in the following examples.



            This would be the answer to "why we assume a Gaussian noise in probabilistic regression or Kalman filter?" too.




            Are there also potential problems associated with this?




            Yes. When we assume Gaussian, we are simplifying. If our simplification is unjustified, our model will under-perform. At this point, we should search for an alternative assumption. In practice, when we make a new assumption about the least known quantity (based on acquired knowledge or speculation), we could extract that assumption and introduce a new Gaussian one, instead of changing the Gaussian assumption. Here are two examples:



            1. Example in regression (noise). Suppose we have no knowledge about observation $A$ (the least known), thus we assume $A sim N(mu, sigma^2)$. After fitting the model, we may observe that the estimated variance $hatsigma^2$ is high. After some investigation, we may assume that $A$ is a linear function of measurement $B$, thus we extract this assumption as $A = colorblueb_1B +c + epsilon_1$, where $epsilon_1 sim N(0, sigma_1^2)$ is the new "the least known". Later, we may find out that our linearity assumption is also weak since, after fitting the model, the observed $hatepsilon_1 = A - hatb_1B -hatc$ also has a high $hatsigma_1^2$. Then, we may extract a new assumption as $A = b_1B + colorblueb_2B^2 + c + epsilon_2$, where $epsilon_2 sim N(0, sigma_2^2)$ is the new "the least known", and so on.


            2. Example in GAN (latent factor). Upon seeing unrealistic outputs from GAN (knowledge) we may add $colorbluetextmore layers$ between $z$ and the output (extract assumption), in the hope that the new network (or function) with the new $z_2 sim N(0, sigma_2^2)$ would lead to more realistic outputs, and so on.






            share|improve this answer











            $endgroup$

















              0












              $begingroup$


              Why people often choose the input to a GAN (z)
              to be samples from a Gaussian?




              Generally, for two reasons: (1) mathematical simplicity, (2) working well enough in practice. However, as we explain, under additional assumptions the choice of Gaussian could be more justified.



              Compare to uniform distribution. Gaussian distribution is not as simple as uniform distribution but it is not that far off either. It adds "concentration around the mean" assumption to uniformity, which gives us the benefits of parameter regularization in practical problems.



              The least known. Use of Gaussian is best justified for continuous quantities that are the least known to us, e.g. noise $epsilon$ or latent factor $z$. "The least known" could be formalized as "distribution that maximizes entropy for a given variance". The answer to this optimization is $N(mu, sigma^2)$ for arbitrary mean $mu$. Therefore, in this sense, if we assume that a quantity is the least known to us, the best choice is Gaussian. Of course, if we acquire more knowledge about that quantity, we can do better than "the least known" assumption, as will be illustrated in the following examples.



              This would be the answer to "why we assume a Gaussian noise in probabilistic regression or Kalman filter?" too.




              Are there also potential problems associated with this?




              Yes. When we assume Gaussian, we are simplifying. If our simplification is unjustified, our model will under-perform. At this point, we should search for an alternative assumption. In practice, when we make a new assumption about the least known quantity (based on acquired knowledge or speculation), we could extract that assumption and introduce a new Gaussian one, instead of changing the Gaussian assumption. Here are two examples:



              1. Example in regression (noise). Suppose we have no knowledge about observation $A$ (the least known), thus we assume $A sim N(mu, sigma^2)$. After fitting the model, we may observe that the estimated variance $hatsigma^2$ is high. After some investigation, we may assume that $A$ is a linear function of measurement $B$, thus we extract this assumption as $A = colorblueb_1B +c + epsilon_1$, where $epsilon_1 sim N(0, sigma_1^2)$ is the new "the least known". Later, we may find out that our linearity assumption is also weak since, after fitting the model, the observed $hatepsilon_1 = A - hatb_1B -hatc$ also has a high $hatsigma_1^2$. Then, we may extract a new assumption as $A = b_1B + colorblueb_2B^2 + c + epsilon_2$, where $epsilon_2 sim N(0, sigma_2^2)$ is the new "the least known", and so on.


              2. Example in GAN (latent factor). Upon seeing unrealistic outputs from GAN (knowledge) we may add $colorbluetextmore layers$ between $z$ and the output (extract assumption), in the hope that the new network (or function) with the new $z_2 sim N(0, sigma_2^2)$ would lead to more realistic outputs, and so on.






              share|improve this answer











              $endgroup$















                0












                0








                0





                $begingroup$


                Why people often choose the input to a GAN (z)
                to be samples from a Gaussian?




                Generally, for two reasons: (1) mathematical simplicity, (2) working well enough in practice. However, as we explain, under additional assumptions the choice of Gaussian could be more justified.



                Compare to uniform distribution. Gaussian distribution is not as simple as uniform distribution but it is not that far off either. It adds "concentration around the mean" assumption to uniformity, which gives us the benefits of parameter regularization in practical problems.



                The least known. Use of Gaussian is best justified for continuous quantities that are the least known to us, e.g. noise $epsilon$ or latent factor $z$. "The least known" could be formalized as "distribution that maximizes entropy for a given variance". The answer to this optimization is $N(mu, sigma^2)$ for arbitrary mean $mu$. Therefore, in this sense, if we assume that a quantity is the least known to us, the best choice is Gaussian. Of course, if we acquire more knowledge about that quantity, we can do better than "the least known" assumption, as will be illustrated in the following examples.



                This would be the answer to "why we assume a Gaussian noise in probabilistic regression or Kalman filter?" too.




                Are there also potential problems associated with this?




                Yes. When we assume Gaussian, we are simplifying. If our simplification is unjustified, our model will under-perform. At this point, we should search for an alternative assumption. In practice, when we make a new assumption about the least known quantity (based on acquired knowledge or speculation), we could extract that assumption and introduce a new Gaussian one, instead of changing the Gaussian assumption. Here are two examples:



                1. Example in regression (noise). Suppose we have no knowledge about observation $A$ (the least known), thus we assume $A sim N(mu, sigma^2)$. After fitting the model, we may observe that the estimated variance $hatsigma^2$ is high. After some investigation, we may assume that $A$ is a linear function of measurement $B$, thus we extract this assumption as $A = colorblueb_1B +c + epsilon_1$, where $epsilon_1 sim N(0, sigma_1^2)$ is the new "the least known". Later, we may find out that our linearity assumption is also weak since, after fitting the model, the observed $hatepsilon_1 = A - hatb_1B -hatc$ also has a high $hatsigma_1^2$. Then, we may extract a new assumption as $A = b_1B + colorblueb_2B^2 + c + epsilon_2$, where $epsilon_2 sim N(0, sigma_2^2)$ is the new "the least known", and so on.


                2. Example in GAN (latent factor). Upon seeing unrealistic outputs from GAN (knowledge) we may add $colorbluetextmore layers$ between $z$ and the output (extract assumption), in the hope that the new network (or function) with the new $z_2 sim N(0, sigma_2^2)$ would lead to more realistic outputs, and so on.






                share|improve this answer











                $endgroup$




                Why people often choose the input to a GAN (z)
                to be samples from a Gaussian?




                Generally, for two reasons: (1) mathematical simplicity, (2) working well enough in practice. However, as we explain, under additional assumptions the choice of Gaussian could be more justified.



                Compare to uniform distribution. Gaussian distribution is not as simple as uniform distribution but it is not that far off either. It adds "concentration around the mean" assumption to uniformity, which gives us the benefits of parameter regularization in practical problems.



                The least known. Use of Gaussian is best justified for continuous quantities that are the least known to us, e.g. noise $epsilon$ or latent factor $z$. "The least known" could be formalized as "distribution that maximizes entropy for a given variance". The answer to this optimization is $N(mu, sigma^2)$ for arbitrary mean $mu$. Therefore, in this sense, if we assume that a quantity is the least known to us, the best choice is Gaussian. Of course, if we acquire more knowledge about that quantity, we can do better than "the least known" assumption, as will be illustrated in the following examples.



                This would be the answer to "why we assume a Gaussian noise in probabilistic regression or Kalman filter?" too.




                Are there also potential problems associated with this?




                Yes. When we assume Gaussian, we are simplifying. If our simplification is unjustified, our model will under-perform. At this point, we should search for an alternative assumption. In practice, when we make a new assumption about the least known quantity (based on acquired knowledge or speculation), we could extract that assumption and introduce a new Gaussian one, instead of changing the Gaussian assumption. Here are two examples:



                1. Example in regression (noise). Suppose we have no knowledge about observation $A$ (the least known), thus we assume $A sim N(mu, sigma^2)$. After fitting the model, we may observe that the estimated variance $hatsigma^2$ is high. After some investigation, we may assume that $A$ is a linear function of measurement $B$, thus we extract this assumption as $A = colorblueb_1B +c + epsilon_1$, where $epsilon_1 sim N(0, sigma_1^2)$ is the new "the least known". Later, we may find out that our linearity assumption is also weak since, after fitting the model, the observed $hatepsilon_1 = A - hatb_1B -hatc$ also has a high $hatsigma_1^2$. Then, we may extract a new assumption as $A = b_1B + colorblueb_2B^2 + c + epsilon_2$, where $epsilon_2 sim N(0, sigma_2^2)$ is the new "the least known", and so on.


                2. Example in GAN (latent factor). Upon seeing unrealistic outputs from GAN (knowledge) we may add $colorbluetextmore layers$ between $z$ and the output (extract assumption), in the hope that the new network (or function) with the new $z_2 sim N(0, sigma_2^2)$ would lead to more realistic outputs, and so on.







                share|improve this answer














                share|improve this answer



                share|improve this answer








                edited yesterday

























                answered Mar 17 at 10:58









                EsmailianEsmailian

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