Not quite the same, rip_shuffle does have some contortions to be able to run in-place (I'm still scratching my head about who's running these sorts of high-perf

Not quite the same, rip_shuffle does have some contortions to be able to run in-place (I'm still scratching my head about who's running these sorts of high-performance algorithms with no auxiliary memory available), so if those cost anything they could contribute to the difference.