[julia-users] Multivariate Normal versus Multivariate Normal Canon in Distributions package

[asim]

I am trying to use the multivariate normal canonical form to draw random 
numbers. According to my understanding, the following two functions should 
give the same result over a large number of draws, but I am getting 
different results. What am I doing wrong. 

function ablRegCoeffPostDraw(xtx::Array{Float64, 2}, xty::Array{Float64, 1},
 errorVariance::Float64, priorMean::Array{Float64, 1}, 
priorPrec::Array{Float64, 2})

    postPrec=priorPrec+xtx/errorVariance

    postMean=priorPrec*priorMean+xty/errorVariance
  
    postMean=postPrec\postMean
  
    rand(MvNormal(postMean, inv(postPrec)))
  
end

function ablRegCoeffPostDraw1(xtx::Array{Float64, 2}, xty::Array{Float64, 
1},
 errorVariance::Float64, priorMean::Array{Float64, 1}, 
priorPrec::Array{Float64, 2})

    postPrec=priorPrec+xtx/errorVariance

    postMean=priorPrec*priorMean+xty/errorVariance
  
    postMean=postPrec\postMean
  
    potential=postPrec*postMean
  
    rand(MvNormalCanon(potential, postPrec))
  
end