On a private network you should be able to build the DAG.
I have a private ethereum blockchain with one GETH node and mining and it does build the dag and mine.
download geth and then use the following customgenesis.json file to launch a private network
{
"coinbase" : "0x0000000000000000000000000000000000000001",
"difficulty" : "0x40000",
"extraData" : "",
"gasLimit" : "0x8000000",
"nonce" : "0x0000000000005442",
"mixhash" :
"0x0000000000000000000000000000000000000000000000000000000000000000",
"parentHash" :
"0x0000000000000000000000000000000000000000000000000000000000000000",
"timestamp" : "0x00",
"alloc": {},
"config": {
"chainId": 19,
"homesteadBlock": 0,
"eip155Block": 0,
"eip158Block": 0
}
}
assuming your on a linux/mac and have the above customgenesis.json file in the same folder as geth run the following command
geth --datadir=./mychaindata init customgenesis.json
for windows
geth.exe --datadir=/mychaindata init customgenesis.json
Once geth has written the customgenesis.json file and created the genesis block you can then run
(Linux)
geth --datadir=./mychaindata
Download Ethminer
Etheminer can be found at https://www.cryptocompare.com/mining/guides/how-to-mine-ethereum/
It will download as cpp-ethminer.
Go through set-up wizard
Start Mining or do your benchmark test