Histogram

Design a hardware module for the Histogram problem.

Given a stream of 4-bit values, count how many times each value from 0 through 15 appears.

After the entire input stream has been processed, output the 16 bin counts in order.

Hardware I/O Encoding

• stream is a one-dimensional stream of unsigned 4-bit integers
• the output is a one-dimensional stream of unsigned 12-bit integers
• output position i is the final count for value i
• the output stream always has length 16

Examples

Example 1

• input stream = [0, 1, 0, 2, 1, 0, 15]
• output: [3, 2, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1]

Example 2

• input stream = [4, 4, 4]
• output: [0, 0, 0, 0, 3, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]