性能函数调用与1相乘

Question

Look at this function:

float process(float in) {
  float out = in;

  for (int i = 0; i < 31; ++i) {
    if (biquads_[i]) {
      out = biquads_[i]->filter(out);
    }
  }

  return out;
}

biquads_ is a std::optional<Biquad>[31] .

in this case i check for every optional to check if its not empty, and then call the filter function of biquad, if instead I unconditionally call filter function, changing it to multiply by 1 or simply return the input value, would be more efficient?

Answer 1

Most likely it won't make a shread of difference (guessing somewhat though since your question is not entirely clear). For two reasons: 1) unless the code is going to be used in a very hot path, it won't matter even if one way is a few nanoseconds faster than the other. 2) most likely your compilers optimizer will be clever enough to generate code that performs close-to (if not identical to) the same in both cases. Did you test it? Did you benchmark/profile it? If not; do so - with optimization enabled.

Strive to write clear, readable, maintainable code. Worry about micro-optimization later when you actually have a problem and your profiler points to your function as a hot-spot.