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I don't know how Ethereum verifies the atomicity of the state of a contract in the mining process.
Say I have a greet-counting contract.
If two people call the greet function in (almost) the same time, can both transactions be included in a single block and the counter be incremented by two?
Or only one transaction will included in a block and the other will be left in the queue for the following block? Or, the worst case, the other transaction will even be thrown away?