Author: José Carlos
Date: 15:10:30 04/12/02
Go up one level in this thread
On April 12, 2002 at 15:08:51, Gian-Carlo Pascutto wrote: >To start off, I want you all to take a quick look at the >two following logs. > >The first is from Fritz 7, the second from Shredder 6. > >------------------------------------------------------------------ >26.Rb7+ Kc6 27.R7xb4 Rxb4 28.Bxb4 Kd5 29.Rxd3+ Kc4 30.Re3 Rxe3 > +- (1.78) Depth: 6/17 00:00:00 21kN >26.Rb7+ Kc6 27.R7xb4 Rxb4 28.Bxb4 Kd5 29.Rxd3+ Kc4 30.Re3 Rxe3 31.fxe3 Kxb4 > +- (1.78) Depth: 7/21 00:00:00 46kN >26.Rxf7! > +- (1.81) Depth: 7/21 00:00:01 74kN >26.Rxf7 Re2 27.Rb7+ Kc5 28.Bxb4+ Kc6 29.Rxg7 d2 > +- (1.84) Depth: 7/21 00:00:01 82kN >26.Bxb4! > +- (1.88) Depth: 7/22 00:00:01 113kN >26.Bxb4! > +- (2.03) Depth: 7/22 00:00:01 123kN >26.Bxb4 Rxb4 27.Rb7+ Kc6 28.R7xb4 Re1+ 29.Ka2 d2 > +- (2.16) Depth: 7/22 00:00:01 140kN >26.Bxb4-- > +- (1.88) Depth: 8/22 00:00:02 158kN >26.Bxb4 Rxb4 27.Rb7+ Ka5 28.Ra3+ Ra4 29.Ra7+ Kb6 30.R3xa4 > +- (1.84) Depth: 8/23 00:00:03 196kN >26.Rxf7! > +- (1.88) Depth: 8/23 00:00:03 247kN >26.Rxf7! > +- (2.03) Depth: 8/23 00:00:03 273kN >26.Rxf7 Re2 27.Rb7+ Kc6 28.R7xb4 Rd5 29.Rb6+ Kc7 30.Rb7+ Kd6 31.R3b6+ > +- (2.16) Depth: 8/23 00:00:03 315kN >------------------------------------------------------------------ > 2.00 0:00 +0.28 6.Ne5 O-O (141) 28.2 > 2.00 0:00 +0.30++ 6.Qd3 Nc8 (386) 38.6 > 2.00 0:00 +0.31 6.Qd3 Nbc6 (562) 51.0 > 2.00 0:00 +0.34++ 6.a3 Bxc3+ 7.bxc3 Nf5 (878) 10.8 > 2.00 0:00 +0.37 6.a3 Bxc3+ 7.bxc3 O-O (960) 11.7 > 3.00 0:00 +0.31 6.a3 Bxc3+ 7.bxc3 O-O 8.Qd3 (1.573) 17.2 > 4.00 0:00 +0.17 6.a3 Bxc3+ 7.bxc3 O-O 8.Qd3 d5 9.cxd5 Bxd5 (3.858) 23.6 > 4.00 0:00 +0.18++ 6.Qd3 Bxc3+ 7.bxc3 Bc8 (5.421) 26.9 > 4.00 0:00 +0.18 6.Qd3 O-O 7.Bxe7 Qxe7 8.Ng1 (8.727) 32.9 > 5.00 0:00 +0.10 6.Qd3 O-O 7.a3 Bxc3+ 8.bxc3 f6 9.Bf4 (20.072) 44.1 > 5.00 0:00 +0.11++ 6.a3 Bxc3+ 7.bxc3 Bxf3 8.gxf3 d5 9.cxd5 Nxd5 (20.507) 44.6 > 5.00 0:00 +0.11 6.a3 Bxc3+ 7.bxc3 O-O 8.Rc1 d5 9.cxd5 exd5 (21.549) 44.0 > 5.00 0:00 +0.12++ 6.Qb3 Bxc3+ 7.Qxc3 Bxf3 8.Qxf3 Nd5 9.Bxd8 Kxd8 (26.941) >46.2 > 5.00 0:00 +0.12 6.Qb3 Bxc3+ 7.Qxc3 O-O 8.Bf4 Nbc6 9.Ng1 (30.312) 47.2 > 6.00 0:01 -0.05 6.Qb3 Na6 7.a3 Bxc3+ 8.Qxc3 f6 9.Bf4 O-O (70.114) 55.3 > 6.00 0:01 -0.04++ 6.Qd3 O-O (73.372) 55.5 > 6.00 0:01 -0.03 6.Qd3 O-O 7.a3 Bxc3+ 8.bxc3 Nbc6 9.c5 (85.695) 55.7 > 6.00 0:01 -0.02++ 6.Bxe7 Bxe7 7.e4 Na6 8.Ne5 (110.658) 57.2 > 6.00 0:02 +0.01 6.Bxe7 Bxe7 7.e3 c5 8.Be2 cxd4 9.Qxd4 O-O (119.562) 57.3 > 6.00 0:02 +0.02++ 6.e3 Bxc3+ 7.bxc3 Bxf3 8.gxf3 Nbc6 9.a3 (130.227) 57.7 > 6.00 0:02 +0.15 6.e3 Bxc3+ 7.bxc3 f6 8.Bf4 e5 9.dxe5 O-O 10.exf6 Rxf6 >(141.644) 58.7 > 7.01 0:03 +0.18 6.e3 Bxc3+ 7.bxc3 f6 8.Bf4 e5 9.dxe5 O-O 10.Bd3 (183.860) >60.2 > 8.01 0:05 +0.22 6.e3 Bxc3+ 7.bxc3 f6 8.Bf4 e5 9.dxe5 O-O 10.Bd3 Nbc6 >11.exf6 (330.335) 62.6 >------------------------------------------------------------------ > >As far as we know, these programs are based on PVS frameworks. >(When I'm talking about fail high, I mean on a different than >the first move, not the aspiration window thing) > >So, what's wrong with the picture? > >-> These programs have _no_ false-fail highs! <- > >I spent some time looking at output from Fritz >and Shredder, and I saw zip, nada, niente, nothing. > >Of course, if your program doesn't print the initial >fail high, you wont see false fail highs either, but >then you always have full reliable mainvariations to go >with them. If you look above, you see that this is not >the case. So I presume what they print out is the initial >fail high. > >How is this possible? > >Even worse, there are two other things that are fundamentally >strange: > >1) Fritz seems to use a very (0.05-0.15) small window when >doing the research on the FH move, and opens it up gradually. > >2) Shredder has _variations_ to go with the initial fail-highs > >I thought about (1), and my initial guess was that they do >the small window researches to check whether the move is a >real fail high, be able to reject it without doing an open-window >research, and save some time because of the smaller window. > >That can't be it. If a move would be, say, only 0.03 better, >you'd fail low and have to do another research to figure out >if the move is a real fail high or not. Moreover, the moves >that fail high the first time always end up being the PV. >Essentially, Fritz has no false fail highs. I'm clueless as >to what's happening here. I'm not sure what you mean in this last paragraph, but the behaviour you mention seems logical to me. I'll tell you what I do: when I fail high in a null window search, I don't print anything yet. I open the window a bit (in my case, half the aspiration size), and research with Alpha,Beta+AS/2. I have two search routines, one with high prunning level and one "careful search". I use the latter here. If the search returns something above alpha, I know the fail high is good, and print a fail high (with a 1 move pv). Then, I open the window to 150 points above the returned val (val,val+150) and search carefully again. This way, I never print false fail highs, and every fail high becomes the pv, as you described. I guess Fritz is doing something much smarter than what I do, but my example is enough to show it's not a strange behaviour. I can't comment on the Shredder case or MTD(f) because I don't have the needed knowledge. José C.
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