Unless the underlying code has been designed specifically for it (at the cost of some lost performance), it is a somewhat unreasonable expectation for high perf

Unless the underlying code has been designed specifically for it (at the cost of some lost performance), it is a somewhat unreasonable expectation for high performance numerical code to always return the same result across version changes. Even running the same code on different machines, or the same machine with differently aligned data is likely to return different (but equally mathematically valid) results.