qr()
takes the QR decomposition.
# S4 method for ddmatrix
chol2inv(x, size = NCOL(x))
numeric distributed matrices for
number of columns of x
containing the Choleski factorization.
A numeric distributed matrix.
The function returns the inverse of a choleski factored matrix, or the
inverse of crossprod(x)
if qr.R(qr(x))
is passed.