Sorting a matrix according to a matrix of column-wise sorted indices

[stevengj]

@kingoslo

I have a matrix that looks like this:

A = rand(40000000000000,3000000000000000000000000)

Your matrix is obviously not that big; it would be more helpful to give actual runnable examples. Also, you should quote your code. Please read: make it easier to help you

@kingoslo

Now I want to use these indices in the fastest possible way to get the matrix with the columns sorted in that order. How can I do that?

Probably faster just to sort the columns directly, in-place, instead of computing the permutation indices and then applying them. e.g.

for col in eachcol(A)
    sort!(col)
end

or foreach(sort!, eachcol(A)).