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From: Junio C Hamano <gitster@pobox.com>
To: Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org>
Cc: git@vger.kernel.org
Subject: Re: [BUG] Git bisect extends bisecting range on repeated good/bad data
Date: Fri, 13 Dec 2019 10:58:56 -0800	[thread overview]
Message-ID: <xmqq5zikkq6n.fsf@gitster-ct.c.googlers.com> (raw)
In-Reply-To: <473FE927-FC11-46A0-8ABB-7A1FDC8C1A6C@linaro.org> (Maxim Kuvyrkov's message of "Fri, 13 Dec 2019 19:38:05 +0300")

Maxim Kuvyrkov <maxim.kuvyrkov@linaro.org> writes:

> Git bisect may /extend/ bisection range on repeated good/bad data.  Is this expected?

It is not "repeated" that is an issue, but yes this is expected.

The bisection works by finding a mid point to cut the graph into two
pieces of roughly the same size, and the graph is defined by the
set of good commits on the bottom (i.e. "we were told that all these
good commits were good, so there is no point going back the history
beyond any of them") and the single "bad" commit you gave the last.

If you give 'bad' that is in the newer part of the history than the
one that is already known to be bad, then you rewind that single
"bad" commit, to force/allow the machinery to recompute the midpoint
[*1*], and because the area to search would be wider when you do so,
it is very much expected that you'd be offered to test more commits.



[Footnote]

*1* I said force/allow is because allowing the machinery to go back
    and recompute is a way to recover when you gave a "bad" earlier
    by mistake.


  reply	other threads:[~2019-12-13 18:59 UTC|newest]

Thread overview: 3+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-13 16:38 [BUG] Git bisect extends bisecting range on repeated good/bad data Maxim Kuvyrkov
2019-12-13 18:58 ` Junio C Hamano [this message]
2019-12-16 13:22   ` Maxim Kuvyrkov

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