A project (C++11) I am working on involves a block of code that will be run somewhere in the trillions of times. I have an integer parameter B in [1,N] and points 1 = b1 < b2 < ... < bk = N where the code executes a different small block of code depending on which interval [bi, b(i+1)) B lies in. The only value that is changing throughout execution is B. However while the value of the bi's are fixed, they are only determined at runtime.
The naive thing to do is to write a bunch of if and else if statements, which at worst case involves k comparisons. However one can do this in constant time: construct a vector myGotos of size N and on each interval [bi, b(i+1)) store the location of the corresponding code block. Then you just do goto myGotos[B].
The solution above seems to me like it would be on average quicker, but the code would be quite ugly. I was wondering if there is a better way to do this.