Figure 6-6. A hashing function maps the hash value input to a defined range. Part a shows the general hashing algorithm structure; part b shows a classic hashing algorithm. Regardless of the positive integer input, the output will always be between 0 and 9.

A good hash function will yield evenly dispersed outputs. For example, regardless of the hash value, any output is just as likely to occur as any other output. More specifically, if the output range is between 0 and 9, looking at actual outputs, there are just as many 0 values as 1, 2, 3 ... 9 values. Figure 6-7 shows a histogram depicting this near-perfect result.

Figure 6-7. When given random numbers as hash value inputs, even a simple modulus hash function will provide an even distribution of outputs.