The Hash Move is a Move Ordering related issue.
The Hash Move is a move probed from the transposition table, either a best move of a stored PV-node - a PV-move, or a good enough refutation move to cause a cutoff. This move should most importantly searched first  . One may save the move generation at all, if the hash move actually fails high. To guard against rare TT key collisions, one may apply a legality test of the hash move .
- Best Move
- Killer Move
- Mate Killers
- Move Ordering
- Null Move
- Pseudo-Legal Move
- Refutation Move
- Threat Move from null move refutations
- Transposition Table
- TTMove legality checking ? & Killers Move Format? by Mahmoud Uthman, CCC, February 08, 2017 » Killer Move
- tt move vs null move by Erin Dame, CCC, May 27, 2017 » Null Move, Null Move Pruning
- Marginal hash move by Harm Geert Muller, CCC, September 16, 2017