Reading about the proof of work, I got to the data generation part (mainly the DAG) and found it in:
In the ethash it is mentioned that the DAG is generated from a seed, then a 16 MB cache and finally a 1 GB data set. When I ran geth and pyethapp as part o f a private network a new DAG was not generated meaning that the one that the one in the home directory has been used.
Why? Isn't the DAG supposed to be uniquely generated from a seed and then based on block header data, namely the nonce and the mixhash which in this case would be the ones in the custom genesis block?