* 'Minimal' diff-algorithm producing a different result than 'myers', 'patience' and 'histogram' ones
@ 2015-05-12 13:07 Dmitry Malikov
2015-05-24 7:33 ` Jeff King
0 siblings, 1 reply; 2+ messages in thread
From: Dmitry Malikov @ 2015-05-12 13:07 UTC (permalink / raw)
To: git
Good day,
I'm trying to compare 4 different git-diff algorithms and the
'minimal' one is the most vague and non-obvious. The documentation
says "Spend extra time to make sure the smallest possible diff is
produced." - that's all.
By any chance, is there any example of diff when 'minimal' algorithm
produces a different result than a 'myers', 'patience' and 'histogram'
ones?
PS: in case of a question like 'why do you need that?' - it's for
testing purposes of some git wrapper library.
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: 'Minimal' diff-algorithm producing a different result than 'myers', 'patience' and 'histogram' ones
2015-05-12 13:07 'Minimal' diff-algorithm producing a different result than 'myers', 'patience' and 'histogram' ones Dmitry Malikov
@ 2015-05-24 7:33 ` Jeff King
0 siblings, 0 replies; 2+ messages in thread
From: Jeff King @ 2015-05-24 7:33 UTC (permalink / raw)
To: Dmitry Malikov; +Cc: git
On Tue, May 12, 2015 at 03:07:46PM +0200, Dmitry Malikov wrote:
> I'm trying to compare 4 different git-diff algorithms and the
> 'minimal' one is the most vague and non-obvious. The documentation
> says "Spend extra time to make sure the smallest possible diff is
> produced." - that's all.
>
> By any chance, is there any example of diff when 'minimal' algorithm
> produces a different result than a 'myers', 'patience' and 'histogram'
> ones?
I don't know of a simple example offhand, but you can easily generate
all of the patches for a repository with each type by doing:
for i in myers minimal patience histogram; do
git log --diff-algorithm=$i -p >$i
done
In git.git, the output for each type is distinct. You might also find
this thread interesting:
http://thread.gmane.org/gmane.comp.version-control.git/143426
It mentions 717b83117 from git.git, whose minimal diff is over 300 lines
shorter than the non-minimal one. It's not exactly a simple example, but
I suspect you won't find a short case; "minimal" only matters in the
complicated ones.
-Peff
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2015-05-12 13:07 'Minimal' diff-algorithm producing a different result than 'myers', 'patience' and 'histogram' ones Dmitry Malikov
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