softmax regression in c++

#include <iostream>
#include <vector>
#include <cmath>
#include <algorithm>
#include <numeric>
#include <fstream>
#include <sstream>
#include <functional>
double myfunction(double num) {
    return exp(num);
}
template <typename T>
void softmax(const typename::std::vector<T> &v, typename::std::vector<T> &s) {
    double sum=0.0;
    transform(v.begin(), v.end(), s.begin(), myfunction);
    sum=accumulate(s.begin(), s.end(), sum);
    for(size_t i=0; i<s.size(); ++i)
        s.at(i)/=sum;
}
template <typename T>
void hypothesis(const std::vector<std::vector<T> > &theta, const std::vector<T> &feature, std::vector<T> &prb) {
    prb.clear();
    double sum=0.0;
    for(size_t i=0; i<theta.size(); ++i) {
        double inner=0.0;
        inner=inner_product(theta.at(i).begin(), theta.at(i).end(), feature.begin(), inner);
        inner=exp(inner);
        sum+=inner;
    }
    for(size_t i=0; i<theta.size(); ++i) {
        double inner=0.0;
        inner=inner_product(theta.at(i).begin(), theta.at(i).end(), feature.begin(), inner);
        inner=exp(inner);
        prb.push_back(inner/sum);
    }
}
double stringtodouble(const std::string& s) {
    std::istringstream iss(s);
    double num;
    return iss>>num?num:0;
}
int indicator(const int &a, const int &b) {
    if(a==b)
        return 1;
    else
        return 0;
}
void print(int i) {
    std::cout<<i<<" ";
}
double CostFunc(const std::vector<std::vector<double> > &vv_iris, const std::vector<std::vector<double> > &theta) {
    double sum3=0.0;
    for(size_t i=0; i<vv_iris.size(); ++i) {
        double sum1=0.0;
        int k;
        for(size_t j=0; j<theta.size(); ++j) {
            double inner=0.0;
            int b=j+1;
            int indi=indicator(vv_iris.at(i).back(), b);
            if(indi)
                k=j;
            inner=inner_product(vv_iris.at(i).begin(), vv_iris.at(i).end()-1, theta.at(j).begin(), inner);
            sum1+=exp(inner);
        }
        sum1=log(sum1);
        double inner=0.0;
        inner=inner_product(vv_iris.at(i).begin(), vv_iris.at(i).end()-1, theta.at(k).begin(), inner);
        inner-=sum1;
        sum3+=inner;
    }
    sum3/=vv_iris.size();
    return -sum3;
}
void GetThetaGrad(const std::vector<std::vector<double> > &vv_iris, const std::vector<std::vector<double> > &theta, const int j, std::vector<double> &grad_theta) {
    double sum=0.0;
    for(size_t i=0; i<vv_iris.size(); ++i) {
        double sum1=0.0;
        for(size_t k=0; k<theta.size(); ++k) {
            double inner=0.0;
            inner=inner_product(vv_iris.at(i).begin(), vv_iris.at(i).end()-1, theta.at(k).begin(), inner);
            inner=exp(inner);
            sum1+=inner;
        }
        double inner=0.0;
        inner=inner_product(vv_iris.at(i).begin(), vv_iris.at(i).end()-1, theta.at(j).begin(), inner);
        inner=exp(inner);
        sum1=(-1)*inner/sum1;
        int b=j+1;
        int indi=indicator(vv_iris.at(i).back(), b);
        sum1+=indi;
        std::vector<double> v_temp(theta.front().size(), 0);
        transform(vv_iris.at(i).begin(), vv_iris.at(i).end()-1, v_temp.begin(), std::bind1st(std::multiplies<double>(), sum1));
        for(size_t l=0; l<theta.front().size(); ++l) {
            grad_theta.at(l)+=v_temp.at(l);
        }
    }
    for(size_t i=0; i<grad_theta.size(); ++i) {
        grad_theta.at(i)=(-1)*grad_theta.at(i)/vv_iris.size();
    }
}
void ReadDataFromCsv(std::string &filename, std::vector<std::vector<double> > &lines_feat) {
    std::ifstream vm_info(filename.c_str());
    std::string lines, var;
    std::vector<double> row;
    lines_feat.clear();
    while(!vm_info.eof()) {
        getline(vm_info, lines);
        if(lines.empty())
            break;
        std::istringstream stringin(lines);
        row.clear();
        row.push_back(1);
        while(std::getline(stringin, var, ',')) {
            if(var=="Iris-setosa")
                var="1";
            else if(var=="Iris-versicolor")
                var="2";
            else if(var=="Iris-virginica")
                var="3";
            double value=stringtodouble(var);
            row.push_back(value);
        }
        lines_feat.push_back(row);
    }
}
template <class DataType>
void ReadMatFromFile(std::string &filename, std::vector<std::vector<DataType> > &lines_feat) {
    std::ifstream vm_info(filename.c_str());
    std::string lines;
    DataType var;
    std::vector<DataType> row;
    lines_feat.clear();
    while(!vm_info.eof()) {
        getline(vm_info, lines);
        if(lines.empty())
            break;
        std::replace(lines.begin(), lines.end(), ',', ' ');
        std::stringstream stringin(lines);
        row.clear();
        while(stringin >> var) {
            row.push_back(var);
        }
        lines_feat.push_back(row);
    }
}
template <class T>
void Display2DVector(std::vector<std::vector<T> > &vv) {
    for(size_t i=0;i<vv.size();++i) {
        for(typename::std::vector<T>::const_iterator it=vv.at(i).begin();it!=vv.at(i).end();++it) {
            std::cout<<*it<<" ";
        }
        std::cout<<"\n";
    }
    std::cout<<"--------the total rows of the 2DVector is "<<vv.size()<<std::endl;
    std::cout<<"--------the total cols of the 2DVector is "<<vv.front().size()<<std::endl;
}
int main() {
    std::string file("Iris.csv"), weight("theta.csv");;
    std::vector<std::vector<double> > vv_iris;
    std::vector<std::vector<double> > theta;
    ReadDataFromCsv(file, vv_iris);
    ReadMatFromFile(weight, theta);
    Display2DVector(vv_iris);
    Display2DVector(theta);
    double old_cost=CostFunc(vv_iris, theta);
    std::cout<<"the orignal cost: "<<old_cost<<std::endl;
    for(;;) {
        for(size_t i=0; i<theta.size(); ++i) {
            std::vector<double> grad_theta(theta.front().size(), 0);
            GetThetaGrad(vv_iris, theta, i, grad_theta);
            for(size_t j=0; j<grad_theta.size(); ++j) {
                theta.at(i).at(j)=theta.at(i).at(j)-0.05*grad_theta.at(j);
            }
        }
        double new_cost=CostFunc(vv_iris, theta);
        std::cout<<"new_cost: "<<new_cost<<std::endl;
        if(fabs(new_cost-old_cost)<0.000000001)
            break;
        old_cost=new_cost;
    }
    Display2DVector(theta);
    return 0;
}