How to check if given number is divisible of 15 in fastest way?

c++ c performance compiler-optimization integer-division
user2532605 picture user2532605 · Sep 9, 2013 · Viewed 32.2k times · Source

Division in processor takes much time, so I want to ask how to check in fastest way if number is divisible of some other number, in my case I need to check if number is divisible by 15.

Also I've been looking through web and found fun ways to check if number is divisible of some number, but I'm looking for fast option.

NOTE: as division takes much time I'm looking for answer without / and %.

Answer

max picture max · Sep 9, 2013

Obligatory answer for other learners who might come looking for an answer.

if (number % n == 0)

In most cases, you can always do this, trusting the smart modern compilers.

This doesn't mean you get discouraged from learning fun ways though. Check out these links.

Fast divisibility tests (by 2,3,4,5,.., 16)?

Bit Twiddling Hacks

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