Which is better option to use for dividing an integer number by 2?

Question

Which of the following techniques is the best option for dividing an integer by 2 and why?

Technique 1:

x = x >> 1;

Technique

Answer 1

The answer to this will depend on the environment you're working under.

• If you're working on an 8-bit microcontroller or anything without hardware support for multiplication, bit shifting is expected and commonplace, and while the compiler will almost certainly turn x /= 2 into x >>= 1, the presence of a division symbol will raise more eyebrows in that environment than using a shift to effect a division.
• If you're working in a performance-critical environment or section of code, or your code could be compiled with compiler optimization off, x >>= 1 with a comment explaining its reasoning is probably best just for clarity of purpose.
• If you're not under one of the above conditions, make your code more readable by simply using x /= 2. Better to save the next programmer who happens to look at your code the 10 second double-take on your shift operation than to needlessly prove you knew the shift was more efficient sans compiler optimization.

All these assume unsigned integers. The simple shift is probably not what you want for signed. Also, DanielH brings up a good point about using x *= 0.5 for certain languages like ActionScript.