But "pick randomly" just devolves into pro-rata, which already exists in many products and has its own problems (namely that participants show more than they wa

But "pick randomly" just devolves into pro-rata, which already exists in many products and has its own problems (namely that participants show more than they want). The more volume you show in this scheme, the more volume you get filled in - aka pro-rata. I'm not sure what fractional allocation is, perhaps that's what I'm calling pro-rata? At any rate, the allocation method that is chosen is hugely important. It will have a large impact on market microstructure. I find that the discrete mini-auctions are strictly inferior to already existing matching algorithms, as they are really just more complex (read: more gameable by HFT) , yet have the same characteristics of other, more widespread systems.