Hi all,

This is a recap mail from 8 years ago for
https://invent.kde.org/util= ities/kate/-/merge_requests/737

Just in case it's useful...

Best regards

Dominik

---------- Forwarded messag= e ---------
Von: Michal = Humpula <michal.humpula@seznam.cz>
Date: Fr., 17. Jan. 201= 4, 13:12
Subject: Re: using google-diff-match-patch
To: Dominik Hauma= nn <dhaumann@kde.org>
Cc: = <kwrite-devel@kde.org>

And here comes the update

With the little tweaks to cpp code, I was able to push down the execution t= ime
for my test example from 8s to 4s (diff binary is able to execute in 0.5s).=

After this, it seems that most of the time is spent converting from QByteAr= ray
to QString and back and creating temporary QStrings. IMHO this could be spe= ed
up considerably by switching to const QByteArray altogether and just workin= g
with references.

The whole output of the diff process is escaped with
QByteArray::toPercentEncoding, which currently takes half of the execution =
time. But I have no idea, why is that necessary.

For comparison, I've run the same test with python and lua version:

Python: 13s
Lua: 18s
Java: 23s

Seems like general problem with algorithm to me.

On Wednesday 15 of January 2014 13:34:07 Dominik Haumann wrote:
> On Wednesday, January 15, 2014 12:11:24 Michal Humpula wrote:
> > did a quick speed test. Compiled with -O2, Qt4.8.6 (no _FAST_ swi= tches).
> > Testing just diff_main routine
> >
> > Two 3,6k lines cpp files (one kate source file) took 4ms per diff= .
> > Two ~11MB cpp files (100 concatenation off above files) took 3,9s= per
> > diff.
> >
> > The numbers are correct, I've checked that twice. Seems like = it doesn't
> > scale in linear time. Just for compare, the "diff" prog= ram can generate
> > output for the second run in 400ms, so there is definitely a spac= e for
> > improvement.
>
> Run it through `valgrind --tool=3Dcallgrind <app>` and analyze t= he output file
> with kcachegrind.
>
> Or with perf record <app> and then perf report.
>
> Maybe there is some Qt class or similar ill used?
>
> Greetings,
> Dominik
>
> > On Tuesday 14 of January 2014 10:57:27 Neil Fraser wrote:
> > > I have absolutely no objections to any open source use of di= ff match
> > > patch.
> > >
> > > That said, before you invest too heavily in this library, pl= ease
> > > verify that the C++/Qt version of diff match patch meets you= r
> > > performance needs.=C2=A0 I've never been happy with this= port, in my tests
> > > it has performed slower than the JavaScript version.=C2=A0 O= ne of these
> > > days I'd like to replace it with a pure C version.
> > >
> > > On 14 January 2014 05:48, Dominik Haumann <dhaumann@kde.org= > wrote:
> > > > Dear Neil,
> > > >
> > > > I am writing to you on behalf of the KDE/Kate project [= 1]. Kate is an
> > > > advanced text editor under KDE with lots of features fo= r programmers.
> > > >
> > > > One feature is showing a diff. For instance, if a file = changed on
> > > > disk,
> > > > we
> > > > currently launch the external `diff` process to get the= diff of the
> > > > text
> > > > buffer and the file on disk, and then show it graphical= ly.
> > > > However, this is not portable and to some degree slow.<= br> > > > >
> > > > Therefore, we are looking for a C++/Qt solution we can = use to generate
> > > > the
> > > > diff. Since google-diff-match-patch has a C++/Qt interf= ace, it looks
> > > > like
> > > > the perfect match. However, Kate is licensed under &quo= t;LGPL version 2 or
> > > > later".
> > > >
> > > > Is there any chance we are allowed to use google-diff-m= atch-patch?
> > > > As far as we know, the Apache 2 license is incompatible= with LGPLv2.
> > > >
> > > > Would it be possible to put google-diff-match-patch int= o a library,
> > > > and
> > > > then dynamically link the text editor to this library? = Or would that
> > > > still violate licensing?
> > > >
> > > > We're very much interested in finding a solution an= d clarifying
> > > > possible
> > > > licensing conflicts.
> > > >
> > > > CC for reference: kwrite-devel@kde.org
> > > >
> > > > Thanks in advance,
> > > > Dominik & Kate developers
> > > >
> > > > [1] http://kate-editor.org/
> >
> > _______________________________________________
> > KWrite-Devel mailing list
> > KWrite-Devel@kde.org
> > https://mail.kde.org/mailman/= listinfo/kwrite-devel

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