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From: Junio C Hamano <gitster@pobox.com>
To: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Cc: Phillip Wood via GitGitGadget <gitgitgadget@gmail.com>,
	git@vger.kernel.org, Phillip Wood <phillip.wood@dunelm.org.uk>
Subject: Re: [PATCH 1/2] patience diff: remove unnecessary string comparisons
Date: Thu, 06 May 2021 10:32:18 +0900	[thread overview]
Message-ID: <xmqqo8do1wbh.fsf@gitster.g> (raw)
In-Reply-To: <nycvar.QRO.7.76.6.2105051649280.50@tvgsbejvaqbjf.bet> (Johannes Schindelin's message of "Wed, 5 May 2021 16:58:38 +0200 (CEST)")

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:

> Right. I had the same concern. But it does look as if
> `xdl_classify_record()` replaced the possibly non-unique hash values to
> unique sequential identifiers.
>
> I have to admit that the code is unnecessarily hard to read for me:
> https://github.com/git/git/blob/v2.31.1/xdiff/xprepare.c#L110-L157
>
> But I do gather that the loop at
> https://github.com/git/git/blob/v2.31.1/xdiff/xprepare.c#L119-L123
> is called for every line, that it does compare it to every seen line with
> the same hash, and that it exits the loop early if the contents disagree:
>
> 	for (rcrec = cf->rchash[hi]; rcrec; rcrec = rcrec->next)
> 		if (rcrec->ha == rec->ha &&
> 				xdl_recmatch(rcrec->line, rcrec->size,
> 					rec->ptr, rec->size, cf->flags))
> 			break;

Yeah, I arrived at the same conclusion.  Also as Phillip said in a
separate message, Myers side already takes advantage of this same
fact, so I am fine with this change.

Thanks, both.

  parent reply	other threads:[~2021-05-06  1:32 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-05-04  9:25 [PATCH 0/2] A couple of small patience diff cleanups Phillip Wood via GitGitGadget
2021-05-04  9:25 ` [PATCH 1/2] patience diff: remove unnecessary string comparisons Phillip Wood via GitGitGadget
2021-05-05  0:31   ` Junio C Hamano
2021-05-05  9:34     ` Phillip Wood
2021-05-05 14:58     ` Johannes Schindelin
2021-05-05 18:00       ` Phillip Wood
2021-05-06  1:32       ` Junio C Hamano [this message]
2021-05-04  9:25 ` [PATCH 2/2] patience diff: remove unused variable Phillip Wood via GitGitGadget

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