Here’s the problem. In Rstudio, Stan runs one chain at a time but not in parallel. Below is an example. This example uses rstanarm but I had the same problem with regular rstan. I’ve also tried it in the regular R console, and it works fine. The problem is only in Rstudio, and only with paralle…

I will mark your reply as solution. Edit: Unmarked, since the bug is apparently not fixed.

The bug still exists. I’m in R 4.0.2 and Rstudio 1.2.5033 and it still is failing to run parallel chains in rstan. Again, it runs fine in the regular R console.

Mac Catalina 10.15.5 R 4.0.2 RStudio 1.3.959 According to Jonah, it won’t work until a future version of Rstudio.

It should work with the latest “preview” version of RStudio but the bug was just fixed recently so it’s not in an official RStudio release yet.

Ok. If using the preview version of RStudio doesn’t work and you’re desperate, you could try ezStan , which forks a new R process per chain so should be more robust (also has a nicer progress indicator IMO 😋).

Hi–I’m not desperate, as I can just use the non-Rstudio R GUI. I just wanted this to be cleared up before Regression and Other Stories comes out. Andrew

Parallel chains with rstan fails in Rstudio

Interfaces RStan

ssp3nc3r July 1, 2020, 8:31pm 2

It was an RStudio bug: RStudio Viewer with rstan running in parrallel with RStudio 1.3

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Parallel chains with rstan fails in Rstudio

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