question on stratum var diff calculation

[lesjokolat]

hi i am developing a new miner to run against yaamp/yiimp pool types specifically for keccak based algos. i have used what i could get data on for my ptarget calculation but get a large percentage of errors.

ptarget = int(0x00ffff * 2** (8*(0x1e - 3)) / mining_set_difficulty_value)

does anyone have any ideas if my calculation is correct and if not any tips most appreciated!

thanks