How to set MultiPV in Komodo?

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JohnW
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How to set MultiPV in Komodo?

Post by JohnW » Sat Jan 11, 2020 2:56 pm

I purchased Komodo 13.2.5 this week and I was reading the README file that mentions it beating Stockfish 10 in a test match when in MCTS mode and the MultiPV=6. I wanted to experiment with that with some other engines but I don't see any setting in the Engine Parameters(Fritz 17 GUI) called "MultiPV". Can anyone point me in the right direction?

Paloma
Posts: 917
Joined: Thu Dec 25, 2008 8:07 pm

Re: How to set MultiPV in Komodo?

Post by Paloma » Sat Jan 11, 2020 4:35 pm

Klick on the "+" Button to the right of the engine name.

+ increased
- decreased

alternatively right click in the Engine window

lkaufman
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Re: How to set MultiPV in Komodo?

Post by lkaufman » Sat Jan 11, 2020 5:08 pm

Assuming the GUI hasn't changed recently, when you load the engine you should see two magnifying glasses with + and -. Just press the + sign five times and it will display the best six moves (and analysis of each) in infinite mode. That is multipv. But I'm not sure if that carries over to running engine matches; it may be that engine matches in Fritz GUI disable multipv. We used our own tester to run these matches.
Komodo rules!

Alayan
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Full name: Alayan Feh

Re: How to set MultiPV in Komodo?

Post by Alayan » Sat Jan 11, 2020 5:26 pm

Claims of KMCTS besting Stockfish in MultiPV mode are deceptive.

In MultiPV mode, KMCTS do not devote any more resources than usual to search the 2nd best move, 3rd best move, etc. Yes, it can provide moves and an eval for them, but any move beyond the first one will be searched to a smaller and smaller depth ("depth" might not be the correct technical term for KMCTS, but you get the point). Putting MultiPV on doesn't make the engine search those other moves as much as the first. Leela behaves like KMCTS in this regard.

Meanwhile, in MultiPV mode, Stockfish (and almost all other engines) will search further moves to the same depth as the best. Of course, in most positions, this means exploring irrelevant subtrees, wasting time and polluting the hash table. It's even worse when the badly ranked moves provoke fail-lows. When doing a timed blitz game, where getting more depth is critical, this is a big handicap.

One could easily make Stockfish search subsequent moves beyond the first one at lesser depth, when in MultiPV mode. Simply outputting some move and an eval doesn't cost much by itself. Such a trick offers huge time savings, and at bullet-blitz TC makes the 1st move significantly stronger. When experiments were done around this, there was also a large outcry from people using SF for analysis and not wanting this behaviour, so it never went anywhere, because there is no known good compound quality measure for MultiPV.

TL;DR : With MultiPV=6, KMCTS is only beating Stockfish 10 because it's doing the exact same search as with MultiPV=1 and getting big time odds advantage. The flip-side is that the average ordering/eval of the multiPV moves of KMCTS is inferior to Stockfish 10, but of course when playing a match only the 1st move matters.

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Ovyron
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Re: How to set MultiPV in Komodo?

Post by Ovyron » Sat Jan 11, 2020 5:37 pm

Alayan wrote:
Sat Jan 11, 2020 5:26 pm
One could easily make Stockfish search subsequent moves beyond the first one at lesser depth, when in MultiPV mode. Simply outputting some move and an eval doesn't cost much by itself. Such a trick offers huge time savings, and at bullet-blitz TC makes the 1st move significantly stronger.
I'd be very interested in such a version.

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