Issue #
Divisions are expensive operations on modern hardware, so replacing divisions with cheaper operations often results in speed boost.
Actions #
Replace double division with a division and a multiplication.
Relevance #
Double divisions can be replaced with a division and multiplication, according to the following patterns:
- (a / b) / c = a / (b * c)
- a / (b / c) = (a * c) / b
Code examples #
Have a look at the following code:
float calc_div(float a, float b, float c) {
return a / b / c;
}
The expression a / b / c can be rewritten with a single division and a multiplication, like this:
float calc_div(float a, float b, float c) {
return a / (b * c);
}
Note
The compiler does this optimization automatically when -funsafe-math-optimizations compilation flag is provided.
