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# KCC's Quizzes about Golomb rulers

A Golomb ruler is a ruler with a set of marks at integer positions such that no two pairs of marks are at the same distance apart. It has been studied by Salomon W. Golomb, Sidon and Babcock. The theory behind the Golomb set of values are used in radio frequency selection, in radio antenna placement and in current transformers

Each ruler can be characterized by:

1. The first mark is always 0
2. Its order : number of marks
3. Its length : distance between the 2 marks at the extreme sides
4. The ruler is said perfect when all the distances (integer) can be measured from 0 up to its end
5. The ruler is said Optimal if no shorter Golomb ruler of the same order exists

The above right picture shows a Golomb ruler of order 4, length 6 and is perfect and optimal. For example, it can measure all the distances from 0 to 6. 1 between marks 0 and 1, 2 between marks 4 and 6, 3 between marks 1 and 4, 4 between marks 0 and 4, etc… up to 6 between marks 0 and 6

Questions:

1. What are the order and the length following Golomb ruler? Is it perfect and optimal?

2. Find at least one Golomb ruler of order 5 and of length below or equal to 13 and that is optimal.

P.S. If you think there are still colleagues or friends (internal or external) you think who can be interested in those quizzes, please let let them know....

Kuo-Chang

• 1.
Order: 4
Length: 7
Perfect: No (cannot measure 5)
Optimal: No (0, 2, 5, 6)
2.
Marks: 0, 1, 4, 9, 11
Order: 5
Length: 11 <=13
Perfect: No (cannot measure 6)
Optimal: Yes

• Congratulation Mark!

• Thanks to all having tried to answer to this quiz and big applause to the ones having found the right solution:

Solutions:

1. Question 1: The order is 4 (there are 4 marks) and the length is 7. It is not perfect, nor optimal because 5 cannot be measured
2. Question 2 : with marks at 0, 1, 4, 9 and 11 is order 5, length below 13. It is optimal, but not perfect
•  The 4 first winners are:

Again, big congrats to them!