Method and system for verifying a sorter

1. A method of verifying a hardware design for a sorter, the sorter accepting base inputs each of a bit width m, the method comprising:

generating a modified version of the hardware design of the sorter accepting extended inputs with a bit width m+q; and

performing formal verification comprising:

implementing a constraint that q least significant bits of each input in a set of extended inputs represent a unique value; and

formally verifying aspects of the modified version of the hardware design of the sorter for the set of extended inputs.

2. The method according to claim 1 , wherein the step of performing formal verification further comprises:

implementing a constraint that the most significant m bits of each extended input in the set of extended inputs are equal to a respective one of a set of base inputs for an unmodified version of the hardware design of the sorter receiving the set of base inputs; and

wherein formally verifying aspects of the modified version of the hardware design of the sorter for the set of extended inputs comprises formally verifying that the most significant m bits of each sorted output of the modified version of the hardware design of the sorter are equal to a respective output obtained by an unmodified version of the hardware design of the sorter receiving the set of base inputs.

3. The method according to claim 1 , wherein the set of base inputs consists of n inputs, and q≥┌log 2 n┐.

4. The method according to claim 3 , wherein the q least significant bits of each input in the set of extended inputs represent a unique value from 0 to n−1.

5. The method according to claim 3 , wherein q≥n.

6. The method according to claim 5 , wherein the q least significant bits of each input in the set of extended inputs implement a unique one hot encoding.

7. The method according to claim 1 , wherein formally verifying aspects of the modified version of the hardware design of the sorter for the set of extended inputs comprises formally verifying set equality between the set of extended inputs and the set of outputs of the modified version of the hardware design of the sorter.

8. The method according to claim 7 , wherein performing formal verification further comprises formally verifying ordering by either:

further formally verifying aspects of the modified version of the hardware design of the sorter for the set of extended inputs by formally verifying the ordering of the outputs of the modified version of the hardware design of the sorter; or

formally verifying the ordering of the outputs of unmodified version of the hardware design of the sorter.

9. The method according to claim 8 , wherein formally verifying the set equality comprises verifying that each of the outputs appears as an input and optionally formally verifying ordering comprises verifying that the outputs of the modified version of the hardware design of the sorter are in sequence and that neighbouring outputs are not equal.

10. The method according to claim 8 , wherein formally verifying the set equality comprises verifying that each of the inputs appears as an output and optionally formally verifying the ordering comprises verifying that the outputs of the modified version or unmodified version of the hardware design of the sorter are in sequence.

11. The method according to claim 1 , wherein the step of performing formal verification further comprises implementing a constraint that all the inputs in the set of base inputs are valid inputs for the unmodified version of the hardware design of the sorter, and that all the inputs in the set of extended inputs are valid inputs for the modified version of the hardware design of the sorter.

12. A method of manufacturing, using an integrated circuit manufacturing system, an integrated circuit comprising a sorter according to a hardware design for a sorter that has been verified according to claim 1 comprising inputting a computer readable dataset description of said integrated circuit to said integrated circuit manufacturing system.

13. A non-transitory computer readable storage medium having stored thereon computer readable code that causes the method of claim 1 to be performed when the code is run on at least one processor.

14. A system for verifying a hardware design a hardware design for a sorter, the sorter accepting base inputs each of a bit width m, the system comprising:

memory configured to store:

a modified version of the hardware design of the sorter, accepting extended inputs with a bit width m+q; and

a formal verification tool; and

one or more processors configured to performing formal verification, using the formal verification tool, by:

implementing a constraint that q least significant bits of each input in a set of extended inputs represent a unique value; and

formally verifying aspects of the modified version of the hardware design of the sorter for the set of extended inputs.

15. The system according to claim 14 , wherein the one or more processors are configured to perform formal verification, using the formal verification tool, by further:

implementing a constraint that the most significant m bits of each extended input in the set of extended inputs are equal to a respective one of a set of base inputs for an unmodified version of the hardware design of the sorter receiving the set of base inputs; and

formally verifying aspects of the modified version of the hardware design of the sorter for the set of extended inputs comprises formally verifying that the most significant m bits of each sorted output of the modified version of the hardware design of the sorter are equal to a respective output obtained by an unmodified version of the hardware design of the sorter receiving the set of base inputs.

16. The system according to claim 14 , wherein formally verifying aspects of the modified version of the hardware design of the sorter for the set of extended inputs further comprises formally verifying set equality between the set of extended inputs and the set of outputs of the modified version of the hardware design of the sorter.

17. The system according to claim 16 , wherein performing formal verification further comprises formally verifying ordering by either:

further formally verifying aspects of the modified version of the hardware design of the sorter for the set of extended inputs by formally verifying the ordering of the outputs of the modified version of the hardware design of the sorter; or

formally verifying the ordering of the outputs of unmodified version of the hardware design of the sorter.

18. The system according to claim 17 , wherein formally verifying the set equality comprises verifying that each of the outputs appears as an input and optionally formally verifying the ordering comprises verifying that the outputs of the modified version of the hardware design of the sorter are in sequence and that neighbouring outputs are not equal.

19. The system according to claim 17 , wherein formally verifying the set equality comprises verifying that each of the inputs appears as an output and optionally formally verifying the ordering comprises verifying that the outputs of the modified version or unmodified version of the hardware design of the sorter are in sequence.