Lab record 02 · Negamax + alpha-beta

Connect Four

Connect Four is a solved game — the first player wins by opening in the centre. This engine searches by iterative deepening with alpha-beta pruning, a Zobrist transposition table and killer-move ordering. When it says “forced win in 5”, that is proven, not guessed.

Your move

Click a column, or press 1–7 · U undo · R new game Tap a column to drop a disc

You 0

Engine 0

Drawn 0

Discs 0

Search telemetry

Played column: —
Depth reached: —
Nodes searched: —
Think time: —
Throughput: —
Evaluation: —

Play a disc to start the search.

Alpha-beta cuts the tree by proving a branch cannot beat one already found. The transposition table is keyed by an incrementally-updated Zobrist hash, so transposed move orders reuse the same result.

Engine

Think time

More time means more depth, not a different algorithm. At “punishing” the engine usually proves the outcome of the whole game well before the board fills.