[R-SIG-Mac] R install on silicon Mac lacks long.double capability

[Naresh Gurbuxani]

Spencer,

I wanted to verify that I have properly installed R.  I was not specifically looking for long double.

Thanks,
Naresh
Sent from my iPhone

> On Oct 23, 2025, at 7:40 PM, Spencer Graves <spencer.graves using prodsyse.com> wrote:
> 
> Naresh:
> 
> 
> May I ask the application that requires long.double?
> 
> 
> Might it make sense to revise the algorithm of the application to get enhanced precision without long.doubles?
> 
> 
> EXAMPLE: Ordinary least squares regression to estimate b in Y = X b + e as b-hat = inverse(X'X) = X'Y. However, computing it that way discards half of the precision. To see that, we write X as its singular value decomposition UDV'. Then X'X = V D^2 V' and X'Y = V D Y. Then inverse(X'X) = inverse(V') inverse(D)^-2 inverse(V) %*% V D U' Y. If you compute that way, you throw away half of the precision of D. You can avoid that by computing inverse(V') inverse(D) U' Y.
> 
> 
> This computation is more commonly done using the QR decomposition, where the loss of numeric precision is equivalent but not as obvious.
> 
> 
> ???
> Please excuse if I have once again exposed my infinite ignorance. Spencer Graves
> 
> 
>> On 10/23/25 17:27, Simon Urbanek wrote:
>> Naresh,
>> Both of those can only be FALSE by definition:
>> 1) arm64 hardware (Apple Silicon, i.e M1,2,3,4) has no support for long doubles, so you cannot enable that one.
>> 2) libxml is always FALSE since 4.2.0 - see ?capabilities:
>>   libxml: is there support for integrating ‘libxml’ with the R event loop?  ‘TRUE’ as from R 3.3.0, ‘FALSE’ as from R 4.2.0.
>> Cheers,
>> Simon
>> PS: what you described in "My installation was in two steps” has no effect on R or its capabilities. Those steps are only required if you want to compile R yourself (or re-compile some packages).
>>>> On 24/10/2025, at 10:35 AM, Naresh Gurbuxani <naresh_gurbuxani using hotmail.com> wrote:
>>> 
>>> On my new macbook pro, I installed R using package installer R-4.5.1-arm64.pkg
>>> My installation lacks long.double and libxml capabilities.  How can these be enabled?
>>> 
>>> My installation was in two steps:
>>> 1.  Install Xcode developer tools (sudo xcode-select install), GNU fortran compiler (gfortran-14.2-universal.pkg at cran), gnu readline, liblzma, and pcre2 (using macports), texlive, and Xquartz.  Install R using above package installer.
>>> 2.  Source install.R from https://mac.r-project.org/bin/.  In sudo R session, run install.libs("r-base-dev").  Reinstall R using above package installer.
>>> 
>>>> capabilities()
>>>       jpeg         png        tiff       tcltk         X11        aqua
>>>       TRUE        TRUE        TRUE        TRUE        TRUE        TRUE
>>>   http/ftp     sockets      libxml        fifo      cledit       iconv
>>>       TRUE        TRUE       FALSE        TRUE        TRUE        TRUE
>>>        NLS       Rprof     profmem       cairo         ICU long.double
>>>       TRUE        TRUE        TRUE        TRUE        TRUE       FALSE
>>>    libcurl
>>>       TRUE
>>>> sessionInfo()
>>> R version 4.5.1 (2025-06-13)
>>> Platform: aarch64-apple-darwin20
>>> Running under: macOS Sequoia 15.4.1
>>> 
>>> Matrix products: default
>>> BLAS:   /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/lib/libRblas.0.dylib
>>> LAPACK: /Library/Frameworks/R.framework/Versions/4.5-arm64/Resources/lib/libRlapack.dylib;  LAPACK version 3.12.1
>>> 
>>> locale:
>>> [1] en_US.UTF-8/en_US.UTF-8/en_US.UTF-8/C/en_US.UTF-8/en_US.UTF-8
>>> 
>>> time zone: America/New_York
>>> tzcode source: internal
>>> 
>>> attached base packages:
>>> [1] stats     graphics  utils     datasets  grDevices methods   base
>>> 
>>> other attached packages:
>>> [1] latticeExtra_0.6-31 lattice_0.22-7      colorspace_2.1-2
>>> 
>>> loaded via a namespace (and not attached):
>>> [1] compiler_4.5.1     deldir_2.0-4       RColorBrewer_1.1-3 Rcpp_1.1.0
>>> [5] interp_1.1-6       jpeg_0.1-11        grid_4.5.1         png_0.1-8
>>>> 
>>> 
>>> nareshgurbuxani$ gfortran --version
>>> GNU Fortran (GCC) 14.2.0
>>> Copyright (C) 2024 Free Software Foundation, Inc.
>>> This is free software; see the source for copying conditions.  There is NO
>>> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
>>> 
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>>> 
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