Find the lowest multiple of some number greater than or equal to some other number.

gistfile1.rb

def foo(n, m)
  return n if n % m == 0
  n + m - (n % m)
end

foo(25, 7) #=> 28 
foo(28, 7) #=> 28 
foo(29, 7) #=> 35

# No branching.
def bar(n, m)
  n + (m - n % m) % m
end

bar(25, 7) #=> 28 
bar(28, 7) #=> 28 
bar(29, 7) #=> 35

gistfile2.rb

require "benchmark"

# ruby 1.9.2p180 (2011-02-18 revision 30909) [i686-linux]

Benchmark.realtime { 1_000_000.times { foo(25, 7) } } #=> 0.4824531078338623
Benchmark.realtime { 1_000_000.times { bar(25, 7) } } #=> 0.42949914932250977

Benchmark.realtime { 1_000_000.times { foo(28, 7) } } #=> 0.3901078701019287
Benchmark.realtime { 1_000_000.times { bar(28, 7) } } #=> 0.43618083000183105

Benchmark.realtime { 1_000_000.times { foo(29, 7) } } #=> 0.4811720848083496
Benchmark.realtime { 1_000_000.times { bar(29, 7) } } #=> 0.43199920654296875