Проецирование массива в память

#include <windows.h>
#include <iostream>
using namespace std;
 
void main()
{
    
    const int n = 2000000; //размерность массива
    i
    
    
    HANDLE hFile=CreateFile(TEXT("stock.dat"), GENERIC_READ|GENERIC_WRITE, 0, NULL, OPEN_ALWAYS, 0, NULL); 
    cout<<"vorher "<<GetFileSize(hFile, NULL)<<endl;    
    
    
    
    HANDLE hMap=CreateFileMapping(hFile, NULL, PAGE_READWRITE, 0, 0, NULL);
    double *arr = new double [n];
    
    for (int i = 0; i<n; i++)
    {
        arr[i] = i+3.44545;
    }
    cout<<arr[2]<<endl;
    arr=(double*)MapViewOfFile(hMap, FILE_MAP_WRITE, 0, 0, 0);
    
    cout<<MapViewOfFile(hMap, FILE_MAP_WRITE, 0, 0, 0);
        
    
    cout<<"nachher "<<GetFileSize(hFile, NULL)<<endl;
    
    
    
    
 
    //UnMapViewOfFile(arr);
    CloseHandle(hMap);
    CloseHandle(hFile);
 
    
    delete [] arr;
 
 
}

arr=(double*)MapViewOfFile(hMap, FILE_MAP_WRITE, 0, 0, 0);