for( int = 4; i != 0; i-- ){..}

for( int = 0; i < 5; i++ ){..}

I possibly remember reading something about a trick for comparing objects to null...

if( null == object ){..}

if( object == null){..}

In C, 0=false, non-zero = true, so, to get the optimization, do this:

for( int i = 4; i; i-- ){..}

The reason this work is because "i" will be true until it hits zero.

And this will be slightly faster because the prefix decrementor is a sliver faster that the suffix decrementor

for( int i = 4; i; --i ){..}

P.S. you had a typo in your code you can't assign a number to "int". I think you meant int i = 4

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Sam Washburn

For example: the Java compiler now automatically uses a stringbuffer object when you concatenate string objects. Java used to do a ton of calculations if you didn't handle it on your own.

I guess you could write a test program both ways and profile it and see which is best.

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Sam Washburn

Also, has anyone ever clocked the use of register variables in for loops? i know register variables aren't a "for sure" thing but i was wonering about averages.

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Sam Washburn

if (object = null) will successfully set your object pointer to null.

if (null = object) will not compile.

So you want to put your null first in the comparison, so if you leave off an '=', your code will not compile and immediately alert you to the mistake.

I'll admit, I do not follow this rule. I still feel more comfortable comparing my known item to a value. I am thinking, "does my item equal such-and-such" as opposed to "does such-and-such equal my item".

of course, I forgot virtually all of C, so I'm going on the knowledge that you said a non-zero is true (including negatives)

I guess you can always watch for these in code, but I'm personally paranoid when it comes to this and would rather have a safty.
and frankly, with todays computers, the difference between a > and a =0 is negligible.
that's really more for the age when we used to code in assembly.
(in a note that none of you would care, I'm taking both a C and Assembly class this semester, so my ignorance shall be partially cured)

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Realm Master: "I'm cockasian"
Soterion Studios

[This message has been edited by ArchAngel (edited January 26, 2007).]

and also i have a question which one is better to use an integer as a flag in your code or a boolean?

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Matthew(22:36-40)"Teacher, which is the greatest commandment in the Law?" Jesus replied: " 'Love the Lord your God with all your heart and with all your soul and with all your mind. This is the first and greatest commandment. And the second is like it: 'Love your neighbor as yourself.All the Law and the Prophets hang on these two commandments."
Whose Son Is the Christ

Is your flag/boolean question in regards to optimization or just asking in general. In general, when creating a new function/method, it is usually a good idea to use a flag. This lets you make updates without changing the interface. Especially important if you have exposed something to customers. But also helps so you don't personally have to rip through all of your code to make each change. It will, of course, most likely require code changes to take advantage of any newly added flags.

As for optimization, I have no clue.

As for optimization, a boolean is just a bit, (which is stored as a byte most of the time.. tsk tsk such a waste). an integer is 4 bytes (a common Int32).
so for a yes or no answer you'd be taking up 4 times as much space as if you were using a boolean.

@arch: generally i think it's bad practice to be changing loop variables.

As for my interest in optimization. If you're working on real-time programs (aka a game) then you want it to run as fast as possible. Just because it runs on your smokin' hot development pc doesn't mean it'll run on someone's Pentium 3. Anyways, thats just one of many reasons for optimization. Overall its just a better practice to write fast code and employers generally like that

quote:

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@arch: generally i think it's bad practice to be changing loop variables.

As for my interest in optimization. If you're working on real-time programs (aka a game) then you want it to run as fast as possible. Just because it runs on your smokin' hot development pc doesn't mean it'll run on someone's Pentium 3. Anyways, thats just one of many reasons for optimization. Overall its just a better practice to write fast code and employers generally like that

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however, would there be a real difference between using the > and using the =0?
isn't the real thing for optimization in the amount of looping you do, and stuff using O(n) and stuff?

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Realm Master: "I'm cockasian"
Soterion Studios

and yes, code should always be readable.

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Realm Master: "I'm cockasian"
Soterion Studios

Although I currently work in a semi-real time environment, we have not had to get to that level of detail. Our output, so far, is fast enough within the necessary time frame.

quote:

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Originally posted by jestermax:
Hey there, i was just thinking about something with regards to code optimization. When you compare values in code, it's actually more efficient to compare it to 0:

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Rule of Optimization: Prototype before polishing. Get it working before you optimize it.

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More in-depth:

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“We should forget about small efficiencies, say about 97% of the time: premature optimization is the root of all evil”. (C. A. R. Hoare)

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I tend to follow these philosophies because I haven't had a need for optimization (except in Bible Dave) as my computer is so fast that it doesn't matter.

EDITs: Fixed formatting

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All Your Base Are Belong To Us!!! chown -r us ./base
"After three days without programming, life becomes meaningless.'' -- Tao of Programming Book 2

[This message has been edited by CPUFreak91 (edited January 27, 2007).]

[This message has been edited by CPUFreak91 (edited January 27, 2007).]

quote:

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Originally posted by jestermax:
you said you weren't sure if optimization was necessary but then your quotes just stated that premature optimization is bad... care to clarify?

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My quotes are trying to start a discussion on premature optimization (and I wasn't entirely sure if you were going to let performance considerations affect the design of your code. (I see that I am wrong). You are right, this did need some clarification... and maybe I should go to bed .

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All Your Base Are Belong To Us!!! chown -r us ./base
"After three days without programming, life becomes meaningless.'' -- Tao of Programming Book 2

The design of your code is the most important part of it and for those just starting out, you'll learn . i'm a bit of a design junkie now; i gave presentations in college about design patterns and development methodologies . Not that i'm boasting knowledge here, i'm just saying its a blast to learn the stuff and its really, really useful to know.

While I agree that premature optimization is evil(figuratively) I also have personally put into practice the post-optimization lessons previously learned in to new code.

I guess what I am saying is stop writing sloppy code and go ahead and optimize ahead of time as long as you a) don't waste your employer's/your own time optimizing things that really don't need to be and b) your code remains readable.

But, that's just my humble opinion and personal practice.

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Sam Washburn

[This message has been edited by samw3 (edited January 27, 2007).]

I use the faster modules in Python (such as cPickle instead of Pickle) and programming methods when there are two options to choose from, as long as they aren't so complex that they appear cryptic, but I don't really pre-optimize my code. If I discover that the code is a noticible resource hog, then I will optimize it.

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All Your Base Are Belong To Us!!! chown -r us ./base
"After three days without programming, life becomes meaningless.'' -- Tao of Programming Book 2

I do believe that after a code base has become relatively stable (v1.0?) to do an optimize version even if there doesn't appear to be any slowdowns on your machine. Again, it a personal practice though, because I don't like bloated code. Another good reason is that others may not have as good a computer as your development box. But, then again, if you code on a 333Mhz and it runs fine, odds are you already have optimized it without realizing.

I've also learned not to trust my best judgment of what needs to be optimized. Profile, profile, profile.

As for interpreted langs, they will suffer the most from slowdowns because of the nature of interpretation, but even compiled code can slow down especially if it is server based. More connections mean more CPU cycles.

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Sam Washburn

[This message has been edited by samw3 (edited January 29, 2007).]

quote:

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Originally posted by samw3:
Well, asking whether you pre-optimize your code is kind of a subjective question.

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I think it comes down to the amount of time you spend on it and how crazy you get about it. You know?

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Like if you are so nit-picky that you spend half a day shaving cycles out of a loop where the time difference is in milliseconds.

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I do believe that after a code base has become relatively stable (v1.0?) to do an optimize version even if there doesn't appear to be any slowdowns on your machine.

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quote:

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Another good reason is that others may not have as good a computer as your development box.

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But, then again, if you code on a 333Mhz and it runs fine, odds are you already have optimized it without realizing.

I've also learned not to trust my best judgment of what needs to be optimized. Profile, profile, profile.

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quote:

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As for interpreted langs, they will suffer the most from slowdowns because of the nature of interpretation

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All Your Base Are Belong To Us!!! chown -r us ./base
"After three days without programming, life becomes meaningless.'' -- Tao of Programming Book 2

quote:

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Originally posted by jestermax:
compiling C++ code is just plain slower then compiling C code (like 5-10 times more) but VS2k5 seems to slow it down even more

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Well, C++ was made for speedy runtime, not compile time. In fact, writing a C++ parser is apparently extremely difficult due to the complexity of the syntax. The compiler with VS2k5 is much more ANSI compliant than 2k3, and is apparently better at catching problems during compilation. All this means slower compilation. You can speed things up a little by using precompiled headers.

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+---------+
|steveth45|
+---------+

on a side topic, i kinda want to write a c compiler. that could be a lot of fun

quote:

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Originally posted by jestermax:
i kinda want to write a c compiler. that could be a lot of fun

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Been there, done that. The hard part is finding someone to show it off to. With regular people you just get the deer-in-the-headlights look, and with other coders you get this why-in-the-world look.

But just in case I just dug up the ancient-and-yet-amazingly-still-applicable link.

http://compilers.iecc.com/crenshaw/

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Sam Washburn

[This message has been edited by samw3 (edited February 03, 2007).]

[This message has been edited by jestermax (edited February 03, 2007).]

...but you never know what happens. One day at work I was tasked with writing an expression analyzer in Java. Oh man was I scared. This was like the ultimate difficult task full of boredom. It actually ended up being quite fun and I still remember that task to this day. It really changed my perspective on the need to learn about compilers. And I've been able to use what I learned from that task in at least encouraging others who have had to do something similar.

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Matthew(22:36-40)"Teacher, which is the greatest commandment in the Law?" Jesus replied: " 'Love the Lord your God with all your heart and with all your soul and with all your mind. This is the first and greatest commandment. And the second is like it: 'Love your neighbor as yourself.All the Law and the Prophets hang on these two commandments."
Whose Son Is the Christ