[求助] 累加的计算精度<le-6 是什么意思?怎么办?

#include<iostream>
#include<cmath>
using namespace std;

double integration(double a, double b, double (*fun)(double));
double f(double);
double g(double);
double h(double);

int main(){
double PI=3.14159;
double half_PI=PI/2;
    cout<<"函数f(x)在[1，3]上的积分为："<<integration(1,3,f)<<endl;
    cout<<"函数g(x)在[0,1]上的积分为："<<integration(0,1,g)<<endl;
    cout<<"函数h(x)在[0，half_PI]上的积分为："<<integration(0,half_PI,h)<<endl;
}

double integration(double a, double b, double (*fun)(double x)){
    double p=0.000001,s=0,s_m=s,l;
    for(int m=1;fabs(s-s_m)<p;m++){
        for(int i=0;i<=m;i++){
             l=(b-a)/m;
             s=s+((*fun)(i*l+a)+(*fun)((i+1)*l+a))*0.5;
        }
    return s;
    }
}
double f(double x){
    return 1/x;
}

double g(double x){
    return exp(x)/(1+exp(x));
}