Warning: There are bugs in the Matrix package.  Specifically,
luDecompose thinks the matrix is singular when it is not.

Note: This directory should really be in a GUIR group space, not
buried inside of gdt.  However, whatever is of use to the group is
probably already in SATIN, and I don't have time to figure out where
the right place to put it is.  Anyway, for it to really be part of
something else, gdt should probably be re-architected.
