Bill Rogers wrote:You got what is expected. It allows you to see what you might gain if you moved twice and nothing more. one halp ply that is all.
Bill
no no no no no... you need to try this before answering. Here is a position searched to depth=12 with null move on and off:
in fact, I can't even get it to search to depth=12 with null=off. It is _way_ more than "a half ply".
here's a paultry 8 ply search:
with null move:
depth time score variation (1)
1 0.00 -0.04 1. ... Kh8
1-> 0.00 -0.04 1. ... Kh8
2 0.00 0.02 1. ... Kh8 2. Bd4
2 0.00 -0.04 1. ... e5 2. Bc3
2-> 0.00 -0.04 1. ... e5 2. Bc3
3 0.00 0.02 1. ... e5 2. Bc3 Kh8
3-> 0.00 0.02 1. ... e5 2. Bc3 Kh8
4 0.00 -0.03 1. ... e5 2. Bc3 Kh8 3. Nb2
4-> 0.00 -0.03 1. ... e5 2. Bc3 Kh8 3. Nb2
5 0.00 0.03 1. ... e5 2. Bc3 Kh8 3. Rac1 Rfe8
5 0.01 -0.04 1. ... Rfd8 2. Bd4 e5 3. Bc3
5-> 0.01 -0.04 1. ... Rfd8 2. Bd4 e5 3. Bc3
6 0.02 -0.03 1. ... Rfd8 2. Bd4 e5 3. Bc3 Kh8 4.
Nb2
6 0.04 -0.05 1. ... Ne5 2. Nxe5 dxe5 3. Qe3 Nd7
6-> 0.04 -0.05 1. ... Ne5 2. Nxe5 dxe5 3. Qe3 Nd7
7 0.06 -0.20 1. ... Ne5 2. Nxe5 dxe5 3. Rd2 Rfd8
4. Rad1 Qd6
7-> 0.07 -0.20 1. ... Ne5 2. Nxe5 dxe5 3. Rd2 Rfd8
4. Rad1 Qd6
8 0.11 -0.21 1. ... Ne5 2. Nxe5 dxe5 3. Rd2 Rfd8
4. Rad1 Qd6 5. Bc2
8 0.15 -1 1. ... Bxe4!!
8 0.17 -0.64 1. ... Bxe4 2. Bxe4 Qxc4 3. Qxc4 Rxc4
4. Nxb6 Rxe4 5. Nxd7 Nxd7
8-> 0.17 -0.64 1. ... Bxe4 2. Bxe4 Qxc4 3. Qxc4 Rxc4
4. Nxb6 Rxe4 5. Nxd7 Nxd7
time=0.17 mat=0 n=232818 fh=93% nps=1.4M
ext-> check=750 1rep=16 mate=0 pp=0 reduce=74K/11K
predicted=0 evals=206K 50move=0 EGTBprobes=0 hits=0
SMP-> splits=0 aborts=0 data=0/128 elap=0.17
and then without:
depth time score variation (1)
1 0.00 -0.04 1. ... Kh8
1-> 0.00 -0.04 1. ... Kh8
2 0.00 0.02 1. ... Kh8 2. Bd4
2 0.01 -0.04 1. ... e5 2. Bc3
2-> 0.01 -0.04 1. ... e5 2. Bc3
3 0.01 0.02 1. ... e5 2. Bc3 Kh8
3-> 0.01 0.02 1. ... e5 2. Bc3 Kh8
4 0.01 -0.03 1. ... e5 2. Bc3 Kh8 3. Nb2
4-> 0.04 -0.03 1. ... e5 2. Bc3 Kh8 3. Nb2
5 0.07 -0.02 1. ... e5 2. Bc3 Kh8 3. Ra2 Rfe8
5 0.17 -0.05 1. ... Nh5 2. Qe3 Bf6 3. Bd4
5-> 0.18 -0.05 1. ... Nh5 2. Qe3 Bf6 3. Bd4
6 0.29 -0.05 1. ... Nh5 2. Qe3 e5 3. Nc3 Nf4 4.
Nd5 Bxd5 5. cxd5 Nxd3 6. Qxd3
6-> 0.87 -0.05 1. ... Nh5 2. Qe3 e5 3. Nc3 Nf4 4.
Nd5 Bxd5 5. cxd5 Nxd3 6. Qxd3
7 1.63 -0.13 1. ... Nh5 2. Qe3 Bf6 3. Bc3 Nc5 4.
Bxf6 Nxf6 5. Nxc5 Qxc5
7-> 3.76 -0.13 1. ... Nh5 2. Qe3 Bf6 3. Bc3 Nc5 4.
Bxf6 Nxf6 5. Nxc5 Qxc5
8 6.56 -0.12 1. ... Nh5 2. Qe3 Bf6 3. Bd4 Bxd4 4.
Qxd4 Nf4 5. Nc3
8 11.51 -1 1. ... Bxe4!!
8 12.14 -0.64 1. ... Bxe4 2. Bxe4 Qxc4 3. Qxc4 Rxc4
4. Nxb6 Rxe4 5. Nxd7 Nxd7
8-> 18.79 -0.64 1. ... Bxe4 2. Bxe4 Qxc4 3. Qxc4 Rxc4
4. Nxb6 Rxe4 5. Nxd7 Nxd7
time=18.79 mat=0 n=29537909 fh=89% nps=1.6M
ext-> check=248K 1rep=17K mate=5K pp=0 reduce=16.6M/255K
predicted=0 evals=27.5M 50move=0 EGTBprobes=0 hits=0
SMP-> splits=0 aborts=0 data=0/128 elap=18.79
It is _way_ more than 1/2 ply...
for 10 seconds, with null gets 16 plies in a test position, without gets 8. You can test this by using "sel=0/0" as a command to turn null-move off in Crafty...
for a 10 second limit, with null=16 plies, without = 8.