Value function clipping in PPO — why and how?

hard

Answer

$L^{\mathrm{VF}}\; = \;\operatorname{max}$
$Prevents value update from swinging wildly per epoch.$
$Modest empirical improvement + more stable.$
$Implementation detail buried in original PPO paper's appendix but has real impact.$

Check yourself — multiple choice

Random
Clip value fn analogously to policy: use max( $(V\; - \;V_{\mathrm{targ}})^{2}$ , $(\mathrm{clip}(V, \;V_{\mathrm{old}}\; \pm \;{\varepsilon})\; - \;V_{\mathrm{targ}})^{2}$ ) → limits value swings per epoch; important PPO detail
Not needed
Same as PPO

PPO value clip: trust-region-style clip on V_θ; important implementation detail.

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