随机梯度下降（Stochastic gradient descent） C++

#include <iostream>
#include <vector>
#include <cmath>
#include <cfloat>

int main() {
    double datax[]={3.4,1.8,4.6,2.3,3.1,5.5,0.7,3.0,2.6,4.3,2.1,1.1,6.1,4.8,3.8};
    double datay[]={26.2,17.8,31.3,23.1,27.5,36.0,14.1,22.3,19.6,31.3,24.0,17.3,43.2,36.4,26.1};
    double cost=DBL_MAX;
    std::vector<double> v_datax,v_datay;
    for(size_t i=0;i<sizeof(datax)/sizeof(datax[0]);++i) {
        v_datax.push_back(datax[i]);
        v_datay.push_back(datay[i]);
    }
   
    int number=v_datax.size();
    double a=0,b=0,error=0;
    while(true) {
        for(std::vector<double>::iterator iterx=v_datax.begin(),itery=v_datay.begin();
        iterx!=v_datax.end(),itery!=v_datay.end();++iterx,++itery) {
            a=a-0.003*(a+b*(*iterx)-*itery);
            b=b-0.003*(a+b*(*iterx)-*itery)*(*iterx);
        }
        error=0;
        for(std::vector<double>::iterator iterx=v_datax.begin(),itery=v_datay.begin();
    iterx!=v_datax.end(),itery!=v_datay.end();++iterx,++itery) {
            error+=(a+b*(*iterx)-*itery)*(a+b*(*iterx)-*itery)*0.5/number;
        }
        if(std::abs(cost-error)<0.0000000000001)
            break;
        cost=error;
    }
    std::cout<<"a = "<<a<<std::endl;
    std::cout<<"b = "<<b<<std::endl;
   
    return 0;
}