Why pointer manipulations are faster

I timed the routine times with a for loop and with a pointer and got a BIG win with the pointer. This type of comparison is easy to do on the avr too, so try it and tell us what you find. What compiler do you use? Thanks for all the responses guys. I'm very new to C Bob so working out how to time the differences between the two will be a good challange and learning experience for me. Just write the function boths ways, call it times or times and print out 'begin' and 'end' and time it with your watch.

In general, if accessing the array in a linear fashion, using a pointer will be quicker. If accessing the array non-linearly then indexed access will likely be quicker.

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I found the trick here, in the web of cprogramming. Well, that is more to the point that in some architectures in this example allows you to store a pointer in a global register. For the most cases in a modern compiler, however, it just gives the compiler one less register to work with, and the compilers these days are pretty darn good at figuring out what to put in a register, and what to not put in a register.

On x86, this would almost certainly cause more problems than it solves as there are only a few 7 at the very most freely usable registers in x Even if almost every line is accessing the global variable it's unlikely to give any enormous benefits then either, since the compiler will be able to load the global pointer at the beginning of the code and then operate on it from then on.

Compilers these days are pretty good at assigning registers the right way, and given a choice, I'd prefer to use the compiler to figure out which register to use when. However, it does work to use global register variables in gcc: Code:. I use pass structs by pointers. That can save up some space. Not sure if this is efficient though. Originally Posted by broli My homepage Advice: Take only as directed - If symptoms persist, please see your debugger Linus Torvalds: "But it clearly is the only right way.

The fact that everybody else does it some other way only means that they are wrong". Originally Posted by iMalc. Don't use the register keyword EVER!

In almost all compilers used nowdays it does nothing whatsoever, and in the ones where is doesn't do nothing you will almost cetainly only make things worse - even if you consider yourself an expert programmer! Originally Posted by matsp. Page 1 of 3 1 2 3 Last Jump to page:.

Replies: 8 Last Post: , AM. Everything works fine and I got the solution I wanted, but specifically I don't understand why this line does manipulate the head? However while this line does not manipulates the head as I am traversing through the list? The head remains [1,2,3,4,5] after every iteration? I read this other stackoverflow explanation on dummy node pointers which was helpful but I still don't understand it. Explanation about dummy nodes and pointers in linked lists. First of all, it is good to see such a clear and easy to read code.

Now, the reason why the following line doesn't work. In python you are working with objects rather than pointers and pointers really aren't that, they are references. Sometimes some variables passed or created are interpreted as objects and sometimes as pointers references. Python doesn't need pointers in order to achieve this as every variable is a reference to an object.

This post discusses how to implement pointers in python, and may give you more information about how to handle them.

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