C# very optimisation

[Ennixo]

hi,

do you know where i can find some ebooks or websites talking about C#
optimisation ?

for exemple, i just learned that ++i is faster than i++. i would like to
know more about the things that can make code faster than fast.

thank you.

[Jon Skeet [C# MVP]]

Ennixo <en****@free.fr > wrote:

do you know where i can find some ebooks or websites talking about C#
optimisation ?

for exemple, i just learned that ++i is faster than i++.
In C#? I don't think so. It *can* be faster in *some* languages, but
it's rarely going to make a significant difference.
i would like to
know more about the things that can make code faster than fast.

Proper design and profiling when necessary, basically. Micro-
optimisations rarely make a significant difference to overall
performance - even if tweaking your code makes one section of code five
times faster, unless a significant amount of time is spent in that part
of the code, it's not going to make much difference. Obviously it
depends on the app, but in many apps these days the most significant
performance bottlenecks come from things like network/database access,
bad choice of threading, etc.

Furthermore, micro-optimisations tend to come at the expense of the
code being as readable as it can be, which IMO should be the primary
goal.

If your app isn't performing well enough, get a profiler and find out
exactly where the bottleneck is. At that point, and only at that point,
should you be really worried about micro-optimisations.

--
Jon Skeet - <sk***@pobox.co m>
http://www.pobox.com/~skeet
If replying to the group, please do not mail me too

[Ennixo]

Jon Skeet [C# MVP] a écrit :

Furthermore, micro-optimisations tend to come at the expense of the
code being as readable as it can be, which IMO should be the primary
goal.

generaly yes, but this is for image processing, so i need to optimize as
much as i can, even if the code becomes 10x bigger and unreadable

[Lebesgue]

When talking about image processing, a VERY big performance bonus can be
gained when using unmanaged (unsafe) code and pointers. I remember an
article saying unmanaged image processing can be up to 28 times faster than
managed.
Here it is
http://tinyurl.com/3sux8
"Ennixo" <en****@free.fr > wrote in message
news:42******** *************@n ews.wanadoo.fr. ..

Jon Skeet [C# MVP] a écrit :

> Furthermore, micro-optimisations tend to come at the expense of the
code being as readable as it can be, which IMO should be the primary
goal.

generaly yes, but this is for image processing, so i need to optimize as
much as i can, even if the code becomes 10x bigger and unreadable

[Ennixo]

Lebesgue a écrit :

When talking about image processing, a VERY big performance bonus can be
gained when using unmanaged (unsafe) code and pointers. I remember an
article saying unmanaged image processing can be up to 28 times faster than
managed.
Here it is
http://tinyurl.com/3sux8

Thank you, i already use unsafe for my processing of course but i would
like to know more about little optimisations now (juste like "++i"
instead of "i++")

but i will read MSDN's unsafe image processing page because i never saw
it before =)

[Søren Reinke]

>

Thank you, i already use unsafe for my processing of course but i would
like to know more about little optimisations now (juste like "++i" instead
of "i++")

++i and i++ is not the same if used within things like calling methods and
stuff like that.

Is the one considered faster than the other ?

--
Søren Reinke
www.Xray-Mag.com/ - Your free diving magazin on the net.
Current issue Diving in North America, 99 pages.
Download it in PDF

[cody]

> for exemple, i just learned that ++i is faster than i++. i would like to

know more about the things that can make code faster than fast.

Where did you read that? There shouldn't be any difference from the
generated code performance.

However, in C# there are similar rules for performance like it is in C++.
The basics in C# are avoiding boxing and use StringBuilder instead of
strings but that shouldn't be useful for image processing anyway.

[Ennixo]

cody a écrit :

Where did you read that? There shouldn't be any difference from the
generated code performance.

i read it in a source code from csharpfr.com and i saw it in some
sources of codeproject.com

[Helge Jensen]

Søren Reinke wrote:

Thank you, i already use unsafe for my processing of course but i would
like to know more about little optimisations now (juste like "++i" instead
of "i++")

Try a profiler, and optimize the places when processing time is actually
used. That way your optimizations may actually matter instead of just
waste your time and make the code unreadable.
++i and i++ is not the same if used within things like calling methods and
stuff like that.
more precicely, ++i and i++ are not the same when used as an expression.
Is the one considered faster than the other ?

When defining your own "operator++ " the x++ variant needs to copy the
old object, ++x does not.

I can't imagine that there is *any* difference whatsoever for the
performance using ++i or i++ (esp. on integral types), and will continue
to think that untill I see a test-program proving otherwise.

--
Helge Jensen
mailto:he****** ****@slog.dk
sip:he********* *@slog.dk
-=> Sebastian cover-music: http://ungdomshus.nu <=-

[Søren Reinke]

"Ennixo" <en****@free.fr > wrote in message
news:42******** *************** @news.free.fr.. .

cody a écrit :

Where did you read that? There shouldn't be any difference from the
generated code performance.

i read it in a source code from csharpfr.com and i saw it in some sources
of codeproject.com

I don't think it matter at all.i++ og ++i just add's 1 to the variable.

But if you have some documentation about it i would love to see it.

--
Søren Reinke
www.Xray-Mag.com/ - Your free diving magazin on the net.
Current issue Diving in North America, 99 pages.
Download it in PDF