fastpath_test.gno

 1package minichess
 2
 3import "testing"
 4
 5// fastPerft walks the tree the way the search does (in-place make/unmake
 6// with the cheap legality and check filters) and cross-checks the filters
 7// against full attack tests at every node.
 8func fastPerft(t *testing.T, e *engine, depth, ply int, inCheck bool) int {
 9	if depth == 0 {
10		return 1
11	}
12	pb := e.buf(ply)
13	e.gen(pb, false)
14	n := 0
15	for i := 0; i < pb.nc+pb.nq; i++ {
16		m := 0
17		if i < pb.nc {
18			m = pb.caps[i]
19		} else {
20			m = pb.quiets[i-pb.nc]
21		}
22		u := e.make(m)
23		fast := e.moveIsLegal(m, u, inCheck)
24		full := !e.attacked(e.kings[1-e.turn], e.turn)
25		if fast != full {
26			t.Fatalf("moveIsLegal mismatch for %s", decode(m))
27		}
28		if full {
29			gc := e.givesCheck(m, u)
30			if gc != e.inCheck() {
31				t.Fatalf("givesCheck mismatch for %s", decode(m))
32			}
33			n += fastPerft(t, e, depth-1, ply+1, gc)
34		}
35		e.unmake(m, u)
36	}
37	return n
38}
39
40func TestFastPathPerft(t *testing.T) {
41	cases := []struct {
42		fen   string
43		depth int
44		want  int
45	}{
46		{"r3k2r/p1ppqpb1/bn2pnp1/3PN3/1p2P3/2N2Q1p/PPPBBPPP/R3K2R w KQkq - 0 1", 2, 2039},
47		{"8/2p5/3p4/KP5r/1R3p1k/8/4P1P1/8 w - - 0 1", 3, 2812},
48		{"r3k2r/Pppp1ppp/1b3nbN/nP6/BBP1P3/q4N2/Pp1P2PP/R2Q1RK1 w kq - 0 1", 3, 9467},
49		{"rnbq1k1r/pp1Pbppp/2p5/8/2B5/8/PPP1NnPP/RNBQK2R w KQ - 1 8", 2, 1486},
50	}
51	for _, c := range cases {
52		p := mustFEN(t, c.fen)
53		e := newEngine(&p)
54		before := p.FEN()
55		if got := fastPerft(t, e, c.depth, 0, e.inCheck()); got != c.want {
56			t.Fatalf("%s: got %d want %d", c.fen, got, c.want)
57		}
58		if after := e.position(p.Fullmove).FEN(); after != before {
59			t.Fatalf("make/unmake did not restore: %s vs %s", after, before)
60		}
61	}
62}