Read Integers using mmap

#include <iostream>
#include <string>
#include <stdio.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <stdlib.h>
#include <unistd.h>
#include <fcntl.h>

using namespace std;

string filepath;
unsigned int READBLOCKSIZE = 1024*1024;
unsigned long long nFileLength = 0;

unsigned long long accumulator = 0; // assuming 32 bit OS running on X86-64

time_t seconds1;
time_t seconds2;

int main(int argc, char *argv[])
{
    if (argc < 2)
    {
        cout << "Please enter a file path\n";
        return -1;
    }

    seconds1 = time (NULL);
    cout << "Start Time in seconds since January 1, 1970 -> " << seconds1 << "\n";

    int fd = fd = open(argv[1], O_RDONLY);
    if(fd == -1) cout << "Could not find/open input file\n";

    struct stat sb;
    if (fstat(fd, &sb) == -1) cout << "Could not get stat on input file\n";          /* To obtain file size */

    off_t pa_offset = 0 & ~(sysconf(_SC_PAGE_SIZE) - 1); // page align from start of file

    char* addr = (char*)mmap(NULL, sb.st_size, PROT_READ, MAP_PRIVATE, fd, pa_offset);
        if (addr == MAP_FAILED) cout << "mmap(2) failed\n";



        cout << "Using One Thread\n"; //**
        //READBLOCKSIZE *= 64;
        char* readBuf = new char[READBLOCKSIZE];
        if(0 == readBuf) return -1;

        unsigned int startOffset = 0;
        if(nFileLength >  READBLOCKSIZE)
        {
            while(startOffset + READBLOCKSIZE < nFileLength)
            {
                int* num = reinterpret_cast<int*>(addr + startOffset);
                for(unsigned int i = 0 ; i < (READBLOCKSIZE/4) ; i++)
                {
                    accumulator += *(num + i);
                }
                startOffset += READBLOCKSIZE;
            }

        }

        if(nFileLength - startOffset > 0)
        {
            int* num = reinterpret_cast<int*>(addr + startOffset);
            for(unsigned int i = 0 ; i < ((nFileLength - startOffset)/4) ; ++i)
            {
                accumulator += *(num + i);
            }
        }
        delete[] readBuf; readBuf = 0;


    seconds2 = time (NULL);
    cout << "End Time in seconds since January 1, 1970 -> " << seconds2 << "\n";
    cout << "Total time to add " << nFileLength/4 << " integers -> " << seconds2 - seconds1 << " seconds\n";

    cout << accumulator << "\n";
    //fclose(pFile);
    return 0;
}