Fix TT write in MultiPV case. #2562
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fixes an error reported earlier as official-stockfish#2404 by @AndyGrant. MultiPV at root shouldn't write to the TT for later lines, as that is neither the eval nor the bestmove for that position. Fixing this error doesn't matter for playing games (http://tests.stockfishchess.org/tests/view/5dcdbd810ebc590256324a11). However, it can lead to wrong mate announcements as reported by @uriblass. In particular the following testcase gives wrong results for the second search, prior to this patch: ``` setoption name MultiPV value 2 position fen 5R2/2kB2p1/p2bR3/8/3p1B2/8/PPP5/2K5 b - - 0 49 go depth 40 position fen 2B2R2/3r2p1/p1kbR3/8/3p1B2/8/PPP5/2K5 b - - 8 48 go depth 40 ``` fixes official-stockfish#2561 Only affects MultiPV search. Bench: 4705960
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Does this also work reliably with multiple Threads? Different Threads may be searching different PV lines as first pv (pvIdx == 0). No? |
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@joergoster yes, I think this is fine in the case of threading as well. Even if threads have a different line a first PV, they will not find/store a mate depth that is wrong. The test case is yielding the right results. |
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Sep 11, 2022
fixes an error reported earlier as official-stockfish#2404 by @AndyGrant. MultiPV at root shouldn't write to the TT for later lines, as that is neither the eval nor the bestmove for that position. Fixing this error doesn't matter for playing games (http://tests.stockfishchess.org/tests/view/5dcdbd810ebc590256324a11). However, it can lead to wrong mate announcements as reported by @uriblass. In particular the following testcase gives wrong results for the second search, prior to this patch: ``` setoption name MultiPV value 2 position fen 5R2/2kB2p1/p2bR3/8/3p1B2/8/PPP5/2K5 b - - 0 49 go depth 40 position fen 2B2R2/3r2p1/p1kbR3/8/3p1B2/8/PPP5/2K5 b - - 8 48 go depth 40 ``` fixes official-stockfish#2561 closes official-stockfish#2562 Only affects MultiPV search. Bench: 4697493
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fixes an error reported earlier as #2404 by @AndyGrant.
MultiPV at root shouldn't write to the TT for later lines, as that is neither the eval nor the bestmove for that position.
Fixing this error doesn't matter for playing games (http://tests.stockfishchess.org/tests/view/5dcdbd810ebc590256324a11).
However, it can lead to wrong mate announcements as reported by @uriblass. In particular the following testcase gives
wrong results for the second search, prior to this patch:
fixes #2561
Only affects MultiPV search.
Bench: 4705960