How do I calculate a tactic when both sides have checks available, a mutual check race?
These answers restate the rules implemented by our open-source engine, which follows the WXF laws and is regression-tested against the official 110-diagram repetition casebook. Where an answer refers to a specific position, that position lives on the linked reference page, where the build verifies it against the engine before publishing.
Direct answer
Work out who runs out of checks, or of anything useful to check with, first, and verify every forced reply exactly rather than assuming your side wins the race. A mutual check exchange, most common in symmetrical positions like 順炮, is unforgiving: a single miscounted step can flip who actually comes out ahead.
Why counting alone is not quite enough
It is tempting to simply count available checks on each side and assume whoever has more wins, but a check that achieves nothing beyond forcing a reply is not the same as one that also wins material or improves your position. Weigh what each check in the sequence actually accomplishes, not just whether a check is available.
Do not forget to check your own safety, not just theirs
In the rush of a mutual checking sequence it is easy to calculate only whether your checks land, and forget to verify that your own general survives the exchange too, exactly the discipline described in calculating a forcing sequence without blundering. A line where you deliver the last check but your own general was exposed the whole time is not actually winning.
Related questions
Is this specific to symmetrical openings like 順炮?
Most common there, but a mutual check race can arise in any sharp middlegame where both generals are somewhat exposed at once.
Should I avoid entering one of these if I am not confident calculating it?
Yes, if you cannot verify the sequence cleanly, a quieter continuation is usually safer than gambling on a race you are not sure you win.
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