Performance Genius

[AspDotNetDev]

Better hope Julian Assange doesn't get a hold of that leak. :~

[Forum Guidelines]

[Steve Caine]

Definitely. There's no excuse for for ( int i = 0; i < data.Count; i++ ) instead of the obvious, clearly superior and faster for ( int i = 0; i < data.Count; ++i ) ;P

[Sander Rossel]

Isn't there a version 2.5? Thread.Sleep(0); ;P

[Ravi Sant]

another version may come up with something like for ( int i = 0; i < data.Count; container.Add(data[i].Items,i++ )

[BillW33]

Yes, it is surprising how few C++ programmers know that ++i executes faster than i++ :)

Just because the code works, it doesn't mean that it is good code.

[ely_bob]

The really sad thing is that most programmers don't know that i-- is the fastest way of the four... :-D

I'd blame it on the Brain farts.. But let's be honest, it really is more like a Methane factory between my ears some days then it is anything else...
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"The conversations he was having with himself were becoming ominous."-.. On the radio...

[ghle]

CIDev wrote:

Yes, it is surprising how few C++ programmers know that ++i executes faster than i++ Smile

Look at the assembly and you'll see why. Fewer instructions to execute.:thumbsup:

Gary

[Steve Caine]

Because ++i doesn't have to keep track of/return the previous value of i.

[realJSOP]

Is there some subtle sarcasm going on here? I've never seen "++i" used (in a for loop) - ever. EDIT ========== Just to see if you guys are chain yankin' here, I tried it both ways : 1 million iterations = both completed the iteration in 0.0040002 seconds 10 million iterations = i++ took 0.0350020, and ++i took 0.0340019 seconds

".45 ACP - because shooting twice is just silly" - JSOP, 2010
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You can never have too much ammo - unless you're swimming, or on fire. - JSOP, 2010
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"Why don't you tie a kerosene-soaked rag around your ankles so the ants won't climb up and eat your candy ass." - Dale Earnhardt, 1997

modified on Sunday, January 2, 2011 9:42 AM

[fjdiewornncalwe]

Does this mean the wife is not up yet as is the case for me and that it is best to let her sleep in on Sunday morning? (Might be a good idea considering she's quick on the draw)... :)

I wasn't, now I am, then I won't be anymore.

[Steve Caine]

John Simmons / outlaw programmer wrote: "Is there some subtle sarcasm going on here? I've never seen "++i" used (in a for loop) - ever." Somewhat subtle. The increment operator is slightly more efficient in its prefix version (++i) because it just increments 'i' and returns its value. The postfix version has to do more work because it returns the *previous* version of 'i', so it has to store that value somewhere before incrementing i. If you're just incrementing 'i', it makes more sense to use the more efficient prefix version. It's just better form, and encourages good habits. (For example, applying it to something more complex than an integer, say an iterator to an STL container class, might produce a more significant performance hit than the miniscule one your test found.) Yet you're right, most of the instances of '++' or' --' I've seen in code, particularly in 'for' loops, is the postfix version. There's no reason for it, yet somehow that has become a near-universal meme in programming. Perhaps because the most common example beginning programmers encounter is the classic C-string copy code snippet, where you really *do* want to use the postfix version:   while (*dst++ = *src++)     ; So I was making a joke that the real coding outrage in the original poster's message was using 'i++' instead of '++i', as if I had completely missed the real outrage of sleeping the thread in each pass through the 'for' loop. (Getting off my soapbox now.)

[yxhu]

improved version of above can be like: for ( int i = 0; i < data.Count; container.Add(data[i++].Items)

[Adrian0]

I can improve even that code for ( int i = 0; i < data.Count; container.Add(data[++i].Items)

[yxhu]

Adrian0, unfortunately, your solution was invalid. As ++i will be calculated(increased) before accessing the element of data collection. container will never have data[0], plus you will receive an out of index exception at the final loop of this for expression. Say data collection has 4 elements. Each iteration looks like: Loop 1, i initialised = 0: container.Add(data[1]).Items Loop 2, i initialised = 1: container.Add(data[2]).Items Loop 3, i initialised = 2: container.Add(data[3]).Items Loop 3, i initialised = 3: container.Add(data[4]).Items <<< Exception here When i++ or ++i is within an expression, ++i has the highest priority to get executed bofere the reset of the expression. In contrast, i++ is get executed after the whole expression has been executed. container.Add(data[i++].Items) //Get the ith element of data collection, append to container and then increase i by 1 container.Add(data[++i].Items) //Increase i by 1, then get the 1th element of data collection to append to the container.

[Adrian0]

Good work yxhu. Didn't recognize that. But if you are that fussy watch your parenthesis

Loop 3, i initialised = 3:
container.Add(data[4]).Items <<< Exception here

Your code wouldn't compile because .Add() is usually of type void. ;) greets Adrian

[yxhu]

Lol... that was a typo. Thanks Adrian0. :thumbsup: