Julia High Performance - Second Edition

Removing the cost of bounds checking

However, as with any extra operation, bound checking has costs too. There are extra operations for all array reads and writes. While this cost is reasonably small and it is usually a good trade-off for safety, in some situations where it can be guaranteed that the array bounds are never crossed, it may be worthwhile to remove these checks. This is possible in Julia using the @inbounds macro as follows:

function prefix_bounds(a, b)    for i in 2:size(a, 1)       a[i] = b[i-1] + b[i]    end end  function prefix_inbounds(a, b)    @inbounds for i in 2:size(a, 1)       a[i] = b[i-1] + b[i]    end end 

The @inbounds macro can be applied in front of a function or loop definition. Once this is done, all bound checking is disabled ...