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OneSpin Solutions
Holiday Puzzler 2018-19

OneSpin’s Holiday Puzzle 2018-19 – The Fibonacci Calculator

Nature is beautiful. And so are numbers, especially the Fibonacci numbers! Well, at least to scientists.

From flowers to pineapples, from bees to human chromosomes, the Fibonacci sequence is a staple in the mathematical modelling of many disparate phenomena of our physical world.

Let’s take honeybees as an example. Did you know that male bees hatch from unfertilized eggs, while females emerge from fertilized ones? Males only have one parent, while females have two. If you trace the pedigree of a male bee, assuming that ancestors are unrelated, you will find that it has one parent, two grandparents, three great-grandparents, five great-great grandparents, and so on. You guessed it: that’s exactly the Fibonacci sequence!

How about designing a simple digital circuit that calculates Fibonacci numbers? We did. It is quite cute. You give it a number n as input and, after some clock cycles, the circuit gives you the nth Fibonacci number as output. We even wrote a bunch of assertions to get confidence that the design is correct. However, we would like to have a design that is not only faster (in terms of clock cycles), but also simpler. You know the drill: they always ask for smaller area, lower power, no bugs, and shorter schedule, but better performance!

What do you say? Can you come up with a better solution? Are you up to the task?


Please fill out the form below to receive the puzzle files for our challenge. They contain a sample design and a formal test bench. Your task is to improve the design, provided that you do not modify the I/O definitions, and that your new design still passes the formal test bench (you cannot change that). There are also some cover properties that you must use to demonstrate how your design performs for the given benchmark.

The cover properties will be used to determine the speed score of your design. Design metrics, like the number of statements, branches, flops, and adders, will be weighted to determine the complexity score of your design. The overall score will be computed automatically using OneSpin. The design with the lowest score wins!

The puzzle files include the equation used to compute the complexity score, and a few additional details. Please carefully read the comments in the two files provided! In the event that something is still not clear, please drop us an email.

The deadline for submission is midnight (CET) on Sunday, January 13th, 2019. Good luck!     


As usual, we have numerous amazing prizes to give away to the following winners:

Head Bee Keeper: Awarded to the solution with the lowest calculated score.

Most Buzzworthy: Awarded to the solution that garners the most votes in a social media “people’s choice” contest.

Italian Mathematician: Awarded at the discretion of the OneSpin jury to a solution that stands out or particularly impresses us.

Bees make delicious honey, of course, but they also pollinate much of the world’s food supply. What more fitting prize for this year’s puzzle than a luxury treat hamper from Fortnum & Mason? Valued at over $150, this delicious assortment of sweet and savory goodies is perfect for sharing with your colleagues, friends, and family—or keep it all to yourself!

Deadline has been passed on Sunday, January 13th, 2019

The winners will be announced by the end of February 2019! Best of luck!