@ricardoV94 That’s what I initially thought as well. I read somewhere that the shape should be (num_chains, num_draws) although I don’t recall where exactly I saw it. But when I tried the shape (num_chains, num_draws) in my code, it crashed. So I instead had to use the shape (num_draws, num_chains). It would be great if someone could revise the documentation of sample_smc to clarify this point.