PH_KILLER_1, // Killer move 1 from the current ply (not used yet).
PH_KILLER_2, // Killer move 2 from the current ply (not used yet).
PH_NONCAPTURES, // Non-captures and underpromotions
PH_KILLER_1, // Killer move 1 from the current ply (not used yet).
PH_KILLER_2, // Killer move 2 from the current ply (not used yet).
PH_NONCAPTURES, // Non-captures and underpromotions