Question

int aNumber;

aNumber = aValue / 2;
aNumber = aValue >> 1;

aNumber = aValue * 2;
aNumber = aValue << 1;

aNumber = aValue / 4;
aNumber = aValue >> 2;

aNumber = aValue * 8;
aNumber = aValue << 3;

// etc.

Whats is the “best” way to do operations? When is better to use bit shifting?

Answer 1

The two are functionally equivalent in the examples you gave (except for the final one, which ought to read aValue * 8 == aValue << 3), if you are using positive integers. This is only the case when multiplying or dividing by powers of 2.

Bit shifting is never slower than arithmetic. Depending on your compiler, the arithmetic version may be compiled down to the bit-shifting version, in which case they both be as efficient. Otherwise, bit-shifting should be significantly faster than arithmetic.

The arithmetic version is often more readable, however. Consequently, I use the arithmetic version in almost all cases, and only use bit shifting if profiling reveals that the statement is in a bottleneck:

Programs should be written for people to read, and only incidentally for machines to execute.