By default, yiimp will adjust the difficulty of your miner automatically over time until you have from 5 to 15 submits per minute. It's a good trade off between bandwidth and accuracy.
You can also set a fixed custom difficulty using the password parameter. For example, if you want to set the difficulty to 64, you would use:
-o stratum+tcp://pool.alpha-mining.fr:3433 -u wallet_adress -p d=64
Voici les valeurs que nous acceptons en diff :
Scrypt, Scrypt-N et Neoscrypt: de 2 à 65536
X11, X13, X14 et X15: de 0.002 à 0.512
Lyra2: de 0.01 à 2048
x16r: de 1 à 61
If the difficulty is set higher than one of the a mined coins, it will be forced down to fit the lowest coin's difficulty.