Obviously not.Zenmastur wrote:I assume that you are stating that the clipped PV leads to the position that produced the current score.syzygy wrote:Clipping of the PV in SF does not make the non-clipped part unreliable.Zenmastur wrote:I don't know if I agree 100%, but I do know that if your dredging your cache for the PV and the time control is long enough that major portions of the cache are over written before the move is made or analysis stopped, the last PV out put is likely to be trashed. This makes it completely unreliable and is a nightmare as far as time is concerned.
The non-clipped part is correct. The clipped part is clipped, so you obviously don't see it. Does not make the clipped part incorrect.
1. That the PV got clipped is NOT an indication that the PV is going to change in the future.I'm saying that the fact that it got clipped in the first place is a good indication that the PV is going to change in the near future.
2. The PV IS going to change in the future.
Sure...Since they are very likely to change it would be foolish to rely on them. Therefore the PV is unreliable.
Rely on them for what?
You have to realise that the value of terminal node of the (non-clipped) PV is based on a call to eval() which is incredibly unreliable.
With SF5? I kind of doubt it.I expect a PV that doesn't have a bad/losing move at ply 2 after a 45-60 ply search. I have run across this condition on several occasions.
Such things happen. Search is a complicated thing. If you know the perfect solution, by all means contribute to SF development.But this issue is a secondary issue. The reason I began saving the PV's in the first place WAS NOT so I could find errors in them. It was the direct result of having the program complete an iteration in just under 4 minutes and then not being able to complete the next iteration in over a hundred hours of analysis. (100*60/4=1500 times as long).
Of course I am simplifying. It seems I got the point across, so it worked.You make it sound like the first half of the PV is perfect and everything that is bad in the PV occurs in the second half. I know that's not true and I suspect that you do as well!
It is only a problem if you want it to be a problem. It is inherent in how alpha-beta search works.The probability of there being an error in the PV at any particular move is a function of its distance from the root position. The exact nature of this function isn't clear to me since, as yet, I haven't kept track of every error and its position in the PV. If I had then I could plot them and or find an equation that mimics their behavior. While this could still be done it would be time consuming. I didn't really think that that level of proof was required to mention it in passing in this forum. This wasn't the reason I started this thread, but it is a problem none the less.