Question

see code, question after.

#include <iostream>
#include <cstdio>

bool prime(unsigned long long num);

int main(){
unsigned long long temp;
unsigned long long max = 600851475143;
FILE * fptr;

try{
fptr = fopen("primes.txt","w");

#pragma omp parallel for
for(unsigned long long i = 2; i<max;i++){
    if(prime(i)){
        temp = i;
        fputs(i + ",",fptr);
        //int percent = (int)((float)i)/((float)max);
        //if(percent > 1 && (percent % 10 == 0)){
        //  std::cout << "Percent Complete: " << percent << std::endl;
        //}
    }
}
std::cout << temp << std::endl;
fclose(fptr);
}catch(...){
    std::cout << "Exception!" << std::endl;
}
return 0;
}

bool prime(unsigned long long num){
for(unsigned long long i = 2;i<num;i++){
    if(num%i == 0)
        return false;
}
return true;
}

@gw runtime failure:

runtime failure:

time failure:

me failure:

ailure:
:

tualQuery failed for %d bytes at address %pQuery failed for %d bytes at address %pery failed
for %d bytes at address %pfailed for %d bytes at address %p for %d bytes at address %pd
bytes at address %pbytes at address %pat address %pddress %press %ppnown pseudo relocation
protocol version %d.

udo relocation protocol version %d.

relocation protocol version %d.

location protocol version %d.

tion protocol version %d.

on protocol version %d.

rotocol version %d.

n %d.
.
Unknown pseudo relocation bit size %d.

nknown pseudo relocation bit size %d.

udo relocation bit size %d.

o relocation bit size %d.

cation bit size %d.

bit size %d.

Why is this runtime failure happening? I’m guessing it has something to do with unsigned long long but I have no idea. Also tried without the omp directive and still same problem.

Answer 1

You made a mistake here:

fputs(i + ",",fptr);

fputs gets const char* as a first argument. You add integer value ‘i’ to a const char* “,” value. This expression i+”,” will point to an invalid memory block as soon as ‘i’ becomes larger then 0 since there is no overloaded operator ‘+’ in C++ which concatenates an integer with a const pointer to a char buffer

You may use the sprintf function instead:

char buf[256] = {0};
sprintf(buf, "%d, ", i);

or, simply fprintf which will put write the string directly to the file

Also, I suggest you to close the file handle outside of the try{ .. }catch block. Otherwise, in case of exception, your file will not be closed at all