[R-pkg-devel] Discovering M1mac cowpads

[J C Nash]

Recently I updated my package nlsr and it passed all the usual checks and was
uploaded to CRAN. A few days later I got a message that I should "fix" my
package as it had failed in "M1max" tests.

The "error" was actually a failure in a DIFFERENT package that was used as
an example in a vignette. I fixed it in my vignette with try(). However, I
am interested in just where the M1 causes trouble.

As far as I can determine so far, for numerical computations, differences will
show up only when a package is able to take advantage of extended precision
registers in the IEEE arithmetic. I think this means that in pure R, it won't
be seen. Packages that call C or Fortran could do so. However, I've not yet
got a good handle on this.

Does anyone have some small, reproducible examples? (For me, reproducing so
far means making a small package and submitting to macbuilder, as I don't
have an M1 Mac.)

Cheers,

John Nash