Perhaps I should treat U as a special case, and give a significant penalty (like nearly one Pawn) for moving a piece that has such a move. Even if it was not an initial move. Because it will always be a wasted move; after it you cannot reach any square that you couldn't reach already. So there must be some tactical reason before considering it.
There is the issue of captures, though, in case of mU. In particular when you are in a location where you have zero captures, like the Shogi hand. My first Shogi engine initially had that flaw: it kept hoarding pieces in hand, because these were worth more there, but this eroded its board control so much that his defenses easily collapsed under attack. So I added a non-linear term that discouraged holding too much material in hand.
Perhaps I should treat U as a special case, and give a significant penalty (like nearly one Pawn) for moving a piece that has such a move. Even if it was not an initial move. Because it will always be a wasted move; after it you cannot reach any square that you couldn't reach already. So there must be some tactical reason before considering it.
There is the issue of captures, though, in case of mU. In particular when you are in a location where you have zero captures, like the Shogi hand. My first Shogi engine initially had that flaw: it kept hoarding pieces in hand, because these were worth more there, but this eroded its board control so much that his defenses easily collapsed under attack. So I added a non-linear term that discouraged holding too much material in hand.