I have a computer with 2 gpus (Intel and Nvidia), i would like to know how i could use both of them to mine Ethers? is it better to use only one gpu or more? and how to calculate the hashrate. does ethereum cpp supports Cuda? Thanks
For the best efficiency, you probably need to run 2 instances of ethminer: one with flags that tell it to use only the AMD card, and a second with flags that tell it to use only the nVidia card.
Genoil's ethminer works with CUDA if your nVidia card doesn't support OpenCL or if you want maximum performance out of it.
As for the flags you need to use, read the manual. Pick the default flags they suggest, then add flags to choose which GPU to run.