This recommendation is part of the open catalog of best practice rules for performance that is automatically detected and reported by Codee.
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.
Related resources
References
Building performance into the code from day one with Codee
