When an engine isn't running "at its best" it usually makes strange blunders a human of the same level would never have; or the opposite.
Maybe it's the only way for programmers to balance the thing a bit.
You can't expect the computer to behave like a human.
"Maybe it's the only way for programmers to balance the thing a bit."
Yes, possibly. I'd expect more recent, commercial engines to be able to play sub-optimally in a more sophisticated way, rather than being accurate 99% of the time but occasionally hanging a pawn to compensate. I almost missed the pawn capture in this game simply because it wasn't the sort of mistake I expected the engine to make.
compt was about 1400-1500 in this game
The engine's play does look pretty pedestrian here I agree, however, in my first two games against it that night - both of which I lost - it was pretty sharp, and able to punish any inaccuracies I made. Perhaps it looks worse here because, as far as I can tell without having submitted the game for computer analysis, I didn't make any major mistakes or blunders for it to capitalize on?
I felt like I had to be totally switched on and aware of any potential threats at all times, or else get destroyed. To be honest, I haven't encountered a 1400-1500 human player who made me feel that amount of pressure :-)
So to win against version 6.2.2 of gnuchess as black:
1. Nf3 Nf6
2. Nc3 d5
3. e3 g6
4. d4 Bg7
5. Ne5 O-O
6. Be2 c5
7. O-O Nbd7
8. f4 e6
9. b3 a6
10. a4 Qc7
11. Qe1 b6
12. Qg3 Bb7
13. Bd2 Rfd8
14. Ra2 Ne8
15. Qh4 Nd6
16. Qf2 Nf6
17. Bf3 Nfe4
18. Nxe4 dxe4
19. Bg4 cxd4
20. exd4 Nf5
21. Bxf5 exf5
22. Rfa1 Rdc8
23. Kh1 b5
24. axb5 axb5
25. Ba5 Qe7
26. Re1 Bd5
27. Raa1 Qb7
28. c4 bxc4
29. bxc4 Bxc4
30. Qe3 Be6
31. Rab1 Qd5
32. Bb6 Rab8
33. h3 Bf8
34. Qg3 Kg7
35. Bc5 Bxc5
36. Rxb8 Rxb8
37. dxc5 f6
38. Rc1 fxe5
39. Qc3 Kf7
40. fxe5 f4
41. c6 e3
42. c7 Ra8
43. Kh2 Ra2
44. Rc2
{White resigns} 0-1
GNU Chess was my first opponent when I began playing a couple of years back. After many frustrating defeats to it on the so-called 'easy' level, I gave up and turned to humankind on this site instead.
Last night, being now a few hundred ELO points better than before, I had another crack at it, this time on the 'normal' level. I lost the first two games, and found the computer's opening play to be highly aggressive, focussing immediately on tactics above development. The third game however I won, much to my surprise as it was 3 a.m. by then :-) Looking back over the game, the computer seemed to make a couple of odd, avoidable blunders, which I don't understand as it's overall level seems to be around 1900-2000 (the 'difficult' level is apparently as high as 2500 depending on hardware, and the 'easy' is around 1500 so this should be a fairly accurate estimate).