Ever since #5094 master only lets the main thread terminate `go mate`
searches, reverting the earlier improvement #1215.
This PR restores the old logic. So any thread that found a "mate in x"
can now stop the search.
To make this work robustly, we need to guard against inexact mate scores
in the best thread selection. In addition, in contrast to time limits,
the main thread may now not complete a d1 search for a mated-in
position.
In master an aborted d1 search may have a PV beginning with
`Move::none()`, in which case no thread selection is performed. See
#623. We fix this bug here by checking if `lastBestPV` is empty or not.
For interrupted d1 searches we now label mated-in scores as inexact.
While at it, we also simplify the logic for detecting if we can
terminate a go mate x search, using the fact that threads.stop can only
be false if we have a completed iteration with a valid score.
The PR has no effect on game play, but should slightly improve general
mate finding and speed up multi-threaded `go mate` searches.
We also add a corresponding matecheck run to the CI. This only involves
61 mates up to mate-in-2. Test runs with the first 50 or 100 mates from
`mates2000.epd` did at times not finish within 30 minutes on my fork or
in local tests, possibly due to search explosions for some mate-in-3
positions.
closes https://github.com/official-stockfish/Stockfish/pull/6668
No functional change
Add runs with --threads 4 to our matetrack CI. These won't be deterministic, of
course. But they may catch early some multithreading bugs in our mate
reporting.
Motivated by #6293 and #6296.
https://github.com/official-stockfish/Stockfish/pull/6297
No functional change.
now checks correctness of PV lines with TB score.
uses 3-4-5 man table bases, downloaded from lichess,
which are cached with the appropriate action.
closes https://github.com/official-stockfish/Stockfish/pull/5500
No functional change
do not upload some unneeded intermediate directories,
disable running authenticated git commands with the checkout action.
Thanks to Yaron A for the report.
closes https://github.com/official-stockfish/Stockfish/pull/5435
No functional change
