Focal loss

$$ {{\rm FL}(p_t) = -(1 - p_t) ^ \gamma {\rm log} (p_t).} $$

$\gamma$はパラメーター

REFERENCES:

  • https://qiita.com/agatan/items/53fe8d21f2147b0ac982
  • https://qiita.com/celaeno42/items/7efdbb1491406f4bde96