The arbitrage we are talking about is the spread. Intertemporal arbitrage, cross-variety arbitrage and cross-market arbitrage. Then there is spot arbitrage, which is not mentioned.

The first is the choice of varieties. It is difficult to arbitrage US crude oil in recent months and far months, because the liquidity of the far-month contract is not enough. Crude oil arbitrage between American crude oil and Brent crude oil is a cross-market operation.

Besides, software arbitrage is either in different contracts, in different varieties or in different markets, and one leg is empty. It can't be that there are multiple orders and empty orders on the same variety. That's locking, not arbitrage. So you don't need to have two accounts to operate.

Even if the trends in recent months and distant months are consistent (in fact, most of the time), there will be strong contracts and weak contracts. There must be a price difference change. It is nothing more than arbitrage opportunities when the price difference changes greatly, and there is no arbitrage opportunity when the price difference changes slightly. That's all.