离散事件模拟在windows和linux中生成不同的结果

我正在进行m/m/2/2离散事件模拟。结果与理论值相同，这意味着程序是正确的（在Ubuntu中，g++）。然而，当我在windows（visualstudio）中再次测试代码时，只有当试用次数少于10000时，结果才是正确的。我调试了很长时间，最后发现我必须使用(double) rand() / ( RAND_MAX + 1 )而不仅仅是(double) rand() / RAND_MAX。

为什么？这两个编译器是否以不同的方式生成随机？

#include <iostream>
#include <stdlib.h>
#include <fstream>
#include <cmath>
#include "iomanip"
#include <queue>
using namespace std;
#define TRIAL_NUM 10000000
//structure that represent a customer
struct cust
{
int cust_id;
double arrival_time;
double depart_time;
};
//uniform random generator
double uniRand()
{
    return (double) rand() / RAND_MAX;
}
//exponential random generator
double expRand(double lam)
{
double u,x;
u=uniRand();
x=(-1/lam)*log(1-u);
return(x);
}
int main()
{
    //seed the random generator
srand (time(NULL));                   
//queue that hold all customers
std::queue<cust*> customers;
double lam = 0, mu = 0;
bool showStatus = false;
cout<<"M/M/1/1 Discrete Event Simulation with "<<TRIAL_NUM<<" customersn"<<" Please spacify the value of lambda:";
cin>>lam;
while(lam<= 0)
{
    cout<<"lambda value must be a positive number, try again:";
    cin>>lam;
}
cout<<"Please specify the value of mu:";
cin>>mu;
while(mu<= 0)
{
    cout<<"lambda value must be a positive number, try again:";
    cin>>mu;
}
cout<<"Show status for each customer? (y/n)";
char show;
cin>>show;
while( tolower(show) != 'y' && tolower(show) != 'n')
{
    cout<<"Invalid input, try again:";
    cin>>show;
}
if ( tolower(show) =='y' )
{
    showStatus = true;
}
//Generating all arrival time, service time for all customers
double temp_time = 1;
cust* temp;
for (int i = 1; i <= TRIAL_NUM; ++i)
{
    temp= new cust;
    temp -> arrival_time = temp_time + expRand(lam);
    temp_time = temp->arrival_time;
    temp->depart_time = temp->arrival_time + expRand(mu);
    temp->cust_id = i;
    customers.push(temp);
}
//Blocking customer count
double block = 0;
bool blockFlag = false;
temp = customers.front();
double server1 = 0, server2 = 0; 
//perform simulation
while( !customers.empty())
{
    if ( server1 < temp->arrival_time)
    {
        server1 = temp->depart_time;
    }
    else if ( server2 < temp->arrival_time)
    {
        server2 = temp->depart_time;
    }
    else
    {
        block++;
        blockFlag = true;
    }
    if (showStatus)
    {
        cout<<"Customer "<<temp->cust_id<<"tarrived at:"<<temp->arrival_time<<"tservice time:"<<temp->depart_time<<"tstatus:";
        if (blockFlag)
        {   
            cout<<"Blocked"<<endl;
        }
        else{
            cout<<"Served"<<endl;
        }
    }
        customers.pop();
        if (!customers.empty())
        {
            temp = customers.front();
        }
        blockFlag = false;
}
cout<<"Blocking probability is: "<<block/TRIAL_NUM<<endl;
return 0;
}