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

by

In every case (including divisible by 2):

if (number % n == 0) do();

Anding with a mask of low order bits is just obfuscation, and with a modern compiler will not be any faster than writing the code in a readable fashion.

If you have to test all of the cases, you might improve performance by putting some of the cases in the if for another: there’s no point it testing for divisibility by 4 if divisibility by 2 has already failed, for example.

More Related Contents:

  1. Why C/C++ is slower than Assembly and other low level languages?
  2. how can i increase the speed of my C++ calculation [closed]
  3. Determine if int is not 0 with no if statements
  4. Why does my code work? Simple arithmetics
  5. How do you set, clear, and toggle a single bit?
  6. Can num++ be atomic for ‘int num’?
  7. How do you get assembler output from C/C++ source in gcc?
  8. Is < faster than
  9. How do I achieve the theoretical maximum of 4 FLOPs per cycle?
  10. What is IACA and how do I use it?
  11. Can’t make value propagate through carry
  12. How to create a byte out of 8 bool values (and vice versa)?
  13. How does photoshop blend two images together? [closed]
  14. Direct way of computing clockwise angle between 2 vectors
  15. How to Detect the Number of Physical Processors / Cores on Windows, Mac and Linux
  16. How do objects work in x86 at the assembly level?
  17. Labels in GCC inline assembly
  18. Efficient 128-bit addition using carry flag
  19. Should I use #define, enum or const?
  20. Math to convert seconds since 1970 into date and vice versa
  21. Does casting to an int after std::floor guarantee the right result?
  22. Compute objects moving with arrows and mouse
  23. Random number generator that produces a power-law distribution?
  24. Special simple random number generator
  25. Convert string to mathematical evaluation [closed]
  26. Inverting a 4×4 matrix
  27. x86 MUL Instruction from VS 2008/2010
  28. How does this bitwise operation check for a power of 2?
  29. How to set, clear, and toggle a single bit?
  30. How can I safely average two unsigned ints in C++?

Leave a Comment