Interview Question 13: Random Number Generation
Random numbers are needed in verification to exercise various corner cases in a test benches. Every test bench is unique. Every test scenario calls for the different kinds of random number generation. Here are two common scenarios encountered in verification. The later question helps is constrained random verification.- Create a function (or task / module) to generate 256 “unique” random numbers.
The generated number is unsigned 8 bit number. A simple $random call may generate repeated numbers. Your task is to create a function which guarantees unique numbers in first set of 256 numbers. The next batch may repeat the whole set.
- Design a module which generates weighted random (pseudo random) numbers. Instead of generating unique numbers this time your task is to generate a small set of numbers randomly distributed but with agreed weight-age Out of all 100 numbers generated the distribution of numbers should be as follows.
Numbers
|
Distribution
|
0
|
5%
|
7
|
20%
|
35
|
25%
|
145
|
30%
|
244
|
20%
|
Total
|
100%
|
