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 <[email protected]>
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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