I guess the best thing would be that it uses a different random seed every time it's run (so that, when re-running the code you'll see similar results which verifies that the result is not sensitive to the seed), but the particular seed that produced the particular results published in a paper is noted.

But still, for code running on different machines, especially for numeric-heavy code that might be running on a particular GPU setup, distributed big data source (where you pull the first available data rather than read in a fixed order), or even on some special supercomputer, it's hard to ask that it be totally reproducible down to the smallest rounding error.