JAGS version 4.3.1 is now available from Sourceforge. This is a patch update with a singular purpose: to allow a new Windows binary to be built using the Rtools42 toolchain.

JAGS is built with the same compiler as R on Windows in order to maintain binary compatibility. Hence we need to recompile JAGS for Windows whenever the compiler used for R changes. The forthcoming release of R 4.2.0 on 22 April features a major change in the compiler used for the Windows version. This change has been well publicized and documented in a series of blog posts by Tomas Kalibera. The fundamental reason for the change is to move to the Microsoft Universal C Runtime (UCRT) which allows native support for UTF-8.

One of the biggest user-visible changes is that the compiler no longer supports 32-bit builds. R 4.2.0 for Windows is 64-bit only and the same is true of JAGS 4.3.1 on Windows. Tomas made the necessary changes to the JAGS installer to make it 64-bit only – as well as fixing a few installer bugs – and these changes are incorporated into JAGS 4.3.1. Many thanks to Tomas for this.

If you are not on Windows then there is absolutely no reason for you to upgrade. The JAGS library and modules are unchanged from the last release. The only changes are in the Windows installer and in the installation documentation.

If you are on Windows then you should delay upgrading JAGS until the release of R 4.2.0 because JAGS 4.3.1 is incompatible with the current release of R.

Apologies to everyone who was hoping for more substantial changes in the next release of JAGS. I promise that JAGS 5.0.0 is on its way.