Fnob: Command Line-Dynamic Random Generator

Design & Verification Conference & Exhibition (DVCon)


Constrained random has been a founding methodology for DV to close coverage within an affordable number of tests. However, there’re several limitations found in current constraint syntax implementation. For example, duplicated code needs to be created for similar tests with different values, introducing error-prone code which is hard to scale. Second, it takes several layers of abstraction to override random behavior for the same variable across the test, which lengthen the schedule hitting the same coverage goal. At last, re-compile is needed for every new random variation added by constraint syntax, which increases turn-around time for test development. An alternative novel way of constrained random called “Fnob” is introduced in this paper to overcome above shortfalls. By providing user freedom to override both random type and value from both command-line and in-line code without re-compile, “Fnob” speeds up coverage closure through less error-prone constrained random coding and faster test development.

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