Non-deterministic behavior in ESOP computation

[aletempiac]

Describe the bug Non-deterministic behavior in ESOP computation in Kitty. Functions esop_from_optimum_pkrm, and esop_from_pprm_slow use an unordered_set data structure to store the cubes. That content is moved to a vector later. Since the order of the cubes in the vector dependents on the compiler, it leads to a non-deterministic behavior.

Environment

• OS: MacOS, Linux, Windows
• Compiler: all the tested ones
• Compilation mode: DEBUG or RELEASE

Check list

• [x] I have tried to run in DEBUG mode and there was no assertion failure (or the reported bug is an assertion failure).
• [x] I have made sure that the provided code compiles and the testcase reproduces the error.
• [x] I have minimized the testcase.

[lee30sonia]

Are the results wrong, or just non-deterministic? In my opinion, producing non-deterministic but correct results is not counted as a "bug", although it is not preferred in an experiment setting. I'm not even sure if non-deterministic is the correct word, if you said the result depends on the compiler. I think non-deterministic means if you run it multiple times on the same machine, the results are different (e.g. when time is used as the random seed, or memory-related bugs depending on the memory address or content being allocated each time). Also, maybe we should put this issue in kitty, not in mockturtle.