Upvote:2
The traditional Calvinistic understanding of the relationship between God's knowledge and God's decree relies on an important distinction, which I'll briefly explain, then present to you how Historically Reformed Confessions articulate the relationship.
When we are talking about "time" before creation, we must understand that "time" in any traditional understanding doesn't make much sense. We cannot say that God went from a state of not knowing all things to a state of knowing all things, nor can we say that there is any meaningful sense in which God had not yet decreed all things, then went on to decree all things.
So when we talk about things happening "in eternity" we must do away with chronological distinctions, and rather talk in term of "logical priority". Which is logically necessary for the other?
Now for the historically Reformed understanding, as presented in the 1689 London Baptist Confession of faith (it's the same in Westminster):
3.2 Although God knoweth whatsoever may or can come to pass, upon all supposed conditions, yet hath he not decreed anything, because he foresaw it as future, or as that which would come to pass upon such conditions.
Let's break this down. In 3.1, the confession says God decreed all things, then here the confession explains that relationship. While it affirms that God knows all things, the confession unequivocally argues that God's decree is not dependent upon that knowledge. God did not decree anything on account of his divine foreknowledge.
Therefore, we would say this "God's decree is logically prior to God's foreknowledge", or alternatively, "God knows all things because he decreed all things."
So this answer is something of a framing challenge, I do not believe you are asking the right question. Whether, as a Calvinist, you affirm Single or Double Predestination, this ought to be your view on this relationship, and it is the view shared by historical Single and Double proponents alike.