Minecraft's respawn grace period can skew results

[DaveyBiggers]

Minecraft appears to have a (not unreasonable) grace period after respawning, during which the agent is invulnerable. This can break experiments if the agent tends to end each mission by dying.

For example, remove lava from the <AgentQuitFromTouchingBlockType> section of cliff_walking_1.xmland then run thetabular_q_learning.pyexample. The agent will quickly die in lava, then be respawned for the next mission. If, in the new mission, it enters lava again before the grace period has expired, it will be able to run around happily for a while, thus breaking the q-table.

[DaveyBiggers]

This is due to EntityPlayerMP.respawnInvulnerabilityTicks - set to 60 at construction. (Equates to 3 seconds at normal game speed.)

Annoyingly private, but easy enough to get around with reflection.