Reading Input from file (Integer array)

How can i read a file, which consists on about 10M integers separated by \n.

I don't know how to use fscanf and i tried reading char by char and converting to int, but it's too slow.

Thanks.

I don't particularly see fscanf being faster than char by char and converting to int. Any reason why this has to be insanely fast ?

But it's really slow, like 1000 int in 3 seconds.

I'm doing the sort-on-disk problem of programming pearls by the way.

I guess the next step would be to see some code. I sort of doubt it's your reading method that's causing slowdown.

Code:

---

        while((c=getc(i)) != EOF)
        {
            if(isdigit(c))
            {
                t = (t*10) + c - '0';
            } else {

                if(t<x*8000000)
                {
                    set(T,t);
                }
                t=0;
            }

        }

---

This is the loop that reads the integers and adds them into a bit array.

The code looks fine -- could be made clearer, but it looks okay. I doubt the slowness is because of this part of the code.

This is the only part executing at the time, besides i used some printf's to count the amount of numbers introduced.

Even set() is nothing really.

Code:

---

void set(char T[],int n)
{
    T[n/8] &= (128 >> (n%8));
}

---

>How can i read a file, which consists on about 10M integers separated by \n.
Use malloc() to create the array, then use:

Code:

---

  long i = 0;
  while (fscanf(fp, "%d", &array[i++]) == 1);

---

And depending on whether you actually need an array, you could just read into an int.

Time this
while((c=getc(i)) != EOF);
Which does nothing, except read the file.

If that's like 99% of the time you're seeing at the moment, then nothing in the loop has any impact on the performance.

15 secons to read thw whole file, which is 114MB