Concept

Propositions and Theorems of Generative Adversarial Networks (GANs)

  • Proposition 1: The optimal discriminator DD for a given generator GG is: Dg(x)=pdata(x)pdata(x)+pg(x)D_g^*(\bold x) = \frac{p_{data}(\bold x)}{p_{data}(\bold x) + p_g(\bold x)}
  • Theorem 1: The global minimum of the virtual training criterion C(G)C(G) is achieved if and only if pg=pdatap_g = p_{data}, having a value of log4-\log 4.
  • Proposition 2: The generative distribution pgp_g converges to pdatap_{data} if:
    1. GG and DD have enough capacity.
    2. At each step of the training algorithm, the discriminator is allowed to reach its optimum given GG.
    3. pgp_g is updated to improve the criterion: Expdata[logDg(x)]+Expg[log(1Dg(x))]\mathbb{E}_{\bold x \sim p_{data}}[\log D_g^*(\bold x)] + \mathbb{E}_{\bold x \sim p_g}[\log(1 - D_g^*(\bold x))]

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Updated 2026-06-15

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Data Science