What's the fastest way to divide an integer by 3?

Question

int x = n / 3;  // <-- make this faster

// for instance

int a = n * 3; // <-- normal integer multiplication

int b = (n << 1) + n; // <-- potentiall         


        

Answer 1

I don't know if it's faster but if you want to use a bitwise operator to perform binary division you can use the shift and subtract method described at this page:

• Set quotient to 0
• Align leftmost digits in dividend and divisor
• Repeat:
  • If that portion of the dividend above the divisor is greater than or equal to the divisor:
    • Then subtract divisor from that portion of the dividend and
    • Concatentate 1 to the right hand end of the quotient
    • Else concatentate 0 to the right hand end of the quotient
  • Shift the divisor one place right
• Until dividend is less than the divisor:
• quotient is correct, dividend is remainder
• STOP