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A general description is here.
A system installation of generic LAPACK 3.10.0 or later will be preferred to the version in the R sources.
‘configure’ option ‘--with-lapack=no’ (equivalently ‘--without-lapack’) forces compilation of the internal LAPACK sources.
If ‘--with-lapack’ is not specified, a system ‘liblapack’ is looked for and used if it reports version 3.10.0 or later and does not contain BLAS routines.
Using 3.10.x may give some different signs from earlier versions in SVDs or eigendecompositions.
Packages using LAPACK will need to be reinstalled if this changes to using an external library.
The set utility functions, notably ‘intersect()’ have been tweaked to be more consistent and symmetric in their two set arguments, also preserving a common ‘mode’.