Reproducibility down to CPU bit differences is a sign that you did something wrong. Usually calculation with insufficient precision and no thought given to the

Reproducibility down to CPU bit differences is a sign that you did something wrong. Usually calculation with insufficient precision and no thought given to the range of simulation error. Simulation must be treated like a measurement, there is a maximum precision for your instrument and you have to know and apply it. And even if you might disagree for the single-threaded case, most things running in parallel will eat that free lunch of bit-identical results due to timing differences.