I made two functions for adding vectors together so that I can add add together sine waves, one of them adds with the + operator and the other uses a lambda function to add them, which makes it easier for me to make functions for multiple operations. one of them takes 5 microseconds, the other takes around 17000.
#include <iostream>
#include <vector>
#include <stdint.h>
#include <numbers>
#include <functional>
#include <chrono>
#include <cmath>
using i16 = int16_t;
constexpr float sample_rate = 44100;
std::vector<i16> sineWave(float frequency, float amplitude, float duration){
int sampleCount = duration*sample_rate;
std::vector<i16> samples(sampleCount);
for(float i = 0;i<sampleCount;i++){
samples[i] = static_cast<i16>(std::sin(2.0f*std::numbers::pi*frequency*(i/sample_rate))*amplitude);
}
return samples;
}
std::vector<i16> waveAdd(std::vector<i16>& wave1, std::vector<i16>& wave2){
if(wave1.size() > wave2.size()){
wave1.resize(wave2.size());
}
else if(wave2.size() > wave1.size()){
wave2.resize(wave1.size());
}
std::vector<i16> final(wave1.size());
for(size_t i = 0;i<wave1.size();i++){
final[i] = wave1[i]+wave2[i];
}
return final;
}
std::vector<i16> waveOperation(std::vector<i16>& wave1, std::vector<i16>& wave2, std::function<i16(i16,i16)> operation){
if(wave1.size() > wave2.size()){
wave1.resize(wave2.size());
}
else if(wave2.size() > wave1.size()){
wave2.resize(wave1.size());
}
std::vector<i16> final(wave1.size());
for(size_t i = 0;i<wave1.size();i++){
final[i] = operation(wave1[i],wave2[i]);
}
return final;
}
int main(){
auto a = sineWave(10000,1000,20);
auto b = sineWave(1000,2000,20);
auto start1 = std::chrono::high_resolution_clock::now();
auto d = waveAdd(a,b);
auto end1 = std::chrono::high_resolution_clock::now();
auto start2 = std::chrono::high_resolution_clock::now();
auto c = waveOperation(a,b,[] (i16 a, i16 b) { return (a+b); } );
auto end2 = std::chrono::high_resolution_clock::now();
auto duration1 = std::chrono::duration_cast<std::chrono::microseconds>(end1-start1);
auto duration2 = std::chrono::duration_cast<std::chrono::microseconds>(end2-start2);
std::cout << "+ operator: " << duration1.count() << std::endl;
std::cout << "lambda: " << duration2.count() << std::endl;
}
Is there a way that I can even this out, or would it be better to just make an equalize length helper function then copy and paste and change the operator?
I did run this in cpp.sh and not on my machine, but I don’t think that makes much of a difference on the time it takes.
>Solution :
is there a way that I can even this out, or would it be better to just make an equalize length helper function then copy and paste and change the operator?
First, understand that std::function carries a runtime performance cost. Its type-erasure is not free!
Second, your lambda function moves compile-time information to runtime. The compiler can optimize multiple adds, but will have a much harder time optimizing multiple calls to an arbitrary std::function::operator().
If you know what lambda you want at compile time, pass it as a template parameter!
template<auto operation>
std::vector<i16> waveOperation(std::vector<i16>& wave1, std::vector<i16>& wave2){
if(wave1.size() > wave2.size()){
wave1.resize(wave2.size());
}
else if(wave2.size() > wave1.size()){
wave2.resize(wave1.size());
}
std::vector<i16> final(wave1.size());
for(size_t i = 0;i<wave1.size();i++){
final[i] = operation(wave1[i],wave2[i]);
}
return final;
}