# Mac OS Catalina 10.15.4 - Rstan: Execution halted

**URL:** <https://discourse.mc-stan.org/t/mac-os-catalina-10-15-4-rstan-execution-halted/15351>\
**Category:** Interfaces\
**Created:** [May 24, 2020, 10:33am UTC](https://discourse.mc-stan.org/t/mac-os-catalina-10-15-4-rstan-execution-halted/15351 "2020-05-24T10:33:59Z")\
**Posts on this page:** 1\
**Showing post:** 2

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**Author:** ![bgoodri](https://yyz2.discourse-cdn.com/flex030/user_avatar/discourse.mc-stan.org/bgoodri/32/4451_2.png) [@bgoodri](https://discourse.mc-stan.org/u/bgoodri)\
**Post date:** [May 24, 2020, 3:56pm UTC](https://discourse.mc-stan.org/t/mac-os-catalina-10-15-4-rstan-execution-halted/15351/2 "2020-05-24T15:56:41Z")

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It is a bug with RStudio when working interactively.

> [@R 4.0.0 and CRAN MacOS binaries](https://discourse.mc-stan.org/t/r-4-0-0-and-cran-macos-binaries/13989/19):
>
> I also was having issues with multiple chains running in parallel in MacOS using latest R-4.0.0 and RStan. I’ve found out that this is a problem of the package parallel from R-4.0.0 I’ve found this [recently issue](https://github.com/rstudio/rstudio/issues/6692) in RStudio’s GitHub that solved my problem: cl \<- parallel::makeCluster(2, setup\_strategy = "sequential") If this works, you could add the following to your ~/.Rprofile until this is fixed in R/RStudio: ## WORKAROUND: https://github.com/rstudio/rstudio/issues/6692 ## Revert to 'se…

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