Re: [HACKERS] git diff --patience
On Fri, Oct 1, 2010 at 7:15 AM, Kevin Grittner wrote: > An interesting exercise it so think about what > real-life lines you could have which would have multiple occurrences > in this pattern, and think about whether you would then prefer the > --patience output, especially if this were part of a larger file. The linux-kernel mailing list had examples of this occurring in real life too. In real C programs function signatures usually end up being the unique lines which is what you want but it can happen that surprising lines are unique. Even braces can be unique if a given indentation level is only used once. The discussion basically convinced me that using uniqueness alone is a bad idea but that the basic idea of trying to identify the important lines is a fine idea. It's just that uniqueness turns out to be a relatively weak signal for interesting lines. Linus suggested line-length but it's pretty debatable which is better. -- greg -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] git diff --patience
Gurjeet Singh wrote: > Alvaro Herrera wrote: >> There is a very simple example posted on some of the blog posts >> that goes something like >> >> >> >> >> >> >> >> xyz >> >> and the "xyz" is moved to the front. In this corner case, the >> patience diff is a lot worse. >> > > Sorry, but that example didn't make much sense to me. Can you > please elaborate, or maybe share those blog posts you are referring to. I tried it out. Here are the results: git diff --color diff --git a/a1 b/a1 index bd0586b..32736d1 100644 --- a/a1 +++ b/a1 @@ -1,7 +1,7 @@ +xyz -xyz git diff --color --patience diff --git a/a1 b/a1 index bd0586b..32736d1 100644 --- a/a1 +++ b/a1 @@ -1,7 +1,7 @@ - - - - - - xyz + + + + + + This is because lines which only occur once in a file are the "anchors" around which lines which occur multiple times move -- after keeping intact any leading and trailing lines which match between the files. An interesting exercise it so think about what real-life lines you could have which would have multiple occurrences in this pattern, and think about whether you would then prefer the --patience output, especially if this were part of a larger file. Even in this supposed "worst case" example, I'm not at all sure I wouldn't prefer --patience, personally, even though more lines are flagged. -Kevin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] git diff --patience
On Fri, Oct 1, 2010 at 9:38 AM, Alvaro Herrera
wrote:
> Excerpts from Kevin Grittner's message of jue sep 30 16:38:11 -0400 2010:
>
> > When I read the description of the algorithm, I can't imagine a
> > situation where --patience would make the diff *worse*. I was
> > somewhat afraid (based on the name) that it would be slow; but
> > if it is slower, it hasn't been by enough for me to notice it.
>
> There is a very simple example posted on some of the blog posts that
> goes something like
>
>
>
>
>
>
>
> xyz
>
> and the "xyz" is moved to the front. In this corner case, the patience
> diff is a lot worse.
>
Sorry, but that example didn't make much sense to me. Can you please
elaborate, or maybe share those blog posts you are referring to.
Regards,
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Re: [HACKERS] git diff --patience
Excerpts from Kevin Grittner's message of jue sep 30 16:38:11 -0400 2010: > When I read the description of the algorithm, I can't imagine a > situation where --patience would make the diff *worse*. I was > somewhat afraid (based on the name) that it would be slow; but > if it is slower, it hasn't been by enough for me to notice it. There is a very simple example posted on some of the blog posts that goes something like xyz and the "xyz" is moved to the front. In this corner case, the patience diff is a lot worse. -- Álvaro Herrera The PostgreSQL Company - Command Prompt, Inc. PostgreSQL Replication, Consulting, Custom Development, 24x7 support -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] git diff --patience
Gurjeet Singh wrote: > The with-patience version has only two hunks, removal of a big > block of comment and addition of a big block of code. > > The without-patience patience is riddled with the mix of two > hunks, spread until line 120. > > --patience is a clear winner here. When I read the description of the algorithm, I can't imagine a situation where --patience would make the diff *worse*. I was somewhat afraid (based on the name) that it would be slow; but if it is slower, it hasn't been by enough for me to notice it. -Kevin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] git diff --patience
Attached are two versions of the same patch, with and without --patience.
The with-patience version has only two hunks, removal of a big block of
comment and addition of a big block of code.
The without-patience patience is riddled with the mix of two hunks, spread
until line 120.
--patience is a clear winner here.
Regards,
On Wed, Sep 29, 2010 at 5:10 PM, Kevin Grittner wrote:
> Peter Eisentraut wrote:
>
> > Do you have an existing commit where you see a difference so I can
> > try it and see if there is some other problem that my local
> > configuration has?
>
> Random poking around in the postgresql.git commits didn't turn up
> any where it mattered, so here's before and after files for the
> example diff files already posted. If you create branch, commit the
> before copy, and copy in the after copy, you should be able to
> replicate the results I posted.
>
> -Kevin
>
>
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>
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diff_without_patience.patch
Description: Binary data
diff_with_patience.patch
Description: Binary data
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Re: [HACKERS] git diff --patience
Peter Eisentraut wrote: > Do you have an existing commit where you see a difference so I can > try it and see if there is some other problem that my local > configuration has? Random poking around in the postgresql.git commits didn't turn up any where it mattered, so here's before and after files for the example diff files already posted. If you create branch, commit the before copy, and copy in the after copy, you should be able to replicate the results I posted. -Kevin predicate.h-before Description: Binary data predicate.h-after Description: Binary data -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] git diff --patience
Peter Eisentraut wrote: > I have tried this switch various times now and haven't seen any > difference at all in the output. Do you have an existing commit > where you see a difference so I can try it and see if there is > some other problem that my local configuration has? Having looked at it more, I find that the output with the switch is usually the same as without; but when they differ, I always have preferred the version with it on. Attached is the diff which caused me to see if there was a way to make the diff output smarter, and the result of adding the --patience flag. This is the unified form that git puts out by default, but the benefit is there after filterdiff --format=context, too. -Kevin patience-off.diff Description: Binary data patience-on.diff Description: Binary data -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] git diff --patience
On ons, 2010-09-15 at 12:58 -0500, Kevin Grittner wrote: > I just discovered the --patience flag on the git diff command, and > I'd like to suggest that we encourage people to use it when possible > for building patches. I just looked at output with and without it > (and for good measure, before and after filterdiff --format=context > for both), and the results were much better with this switch. I have tried this switch various times now and haven't seen any difference at all in the output. Do you have an existing commit where you see a difference so I can try it and see if there is some other problem that my local configuration has? -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
Re: [HACKERS] git diff --patience
Kevin Grittner wrote: > I just discovered the --patience flag on the git diff command, and > I'd like to suggest that we encourage people to use it when possible > for building patches. I just looked at output with and without it > (and for good measure, before and after filterdiff --format=context > for both), and the results were much better with this switch. > > Here's a reference to the algorithm: > > http://bramcohen.livejournal.com/73318.html > > I think that page understates the benefits, though. I have seen the bracket example shown and the --patience output is clearly nicer. -- Bruce Momjian http://momjian.us EnterpriseDB http://enterprisedb.com + It's impossible for everything to be true. + -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
[HACKERS] git diff --patience
I just discovered the --patience flag on the git diff command, and I'd like to suggest that we encourage people to use it when possible for building patches. I just looked at output with and without it (and for good measure, before and after filterdiff --format=context for both), and the results were much better with this switch. Here's a reference to the algorithm: http://bramcohen.livejournal.com/73318.html I think that page understates the benefits, though. -Kevin -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers
