# Efficient computation of the matrix square root inverse

A common problem in statistics is computing the square root inverse of a symmetric positive definite matrix. What would be the most efficient way of computing this?

I came across some literature (which I haven't read yet), and some incidental R code here, which I will reproduce here for convenience

# function to compute the inverse square root of a matrix
fnMatSqrtInverse = function(mA) {
ei = eigen(mA)