two phone screens. some interviewers were nice and others were more strict, lots of interesting math and research discussed. got asked a flurry of technicals, ramping up in difficulty each time, and even some open ended questions where they explicitly said there is no interview-tractable solution and just wanted to hear my ideas for an approach

HR phone call, tech phone call, then on site visit. No food or breaks provided, pretty exhausting by the end when you meet with the manager who I would never speak highly about.