omp parallel for in Conv3D and ConvGrad3D

You must modify this op c_compile_args() method to call super. Otherwise, the -fopenmp parameter won't be set. That also probably mean that your speed up in your timming don't come from this, but from the parallel gemv.

On that side, I don't like having this by default, as most people will have a parallel blas. This mean that we would need to detect here is blas is parallel or not. Do you have a suggestion? Can you confirm that the speed up was from the parallel blas and not that line?

I think we need to keep the line in the case where there is no blas. I'm not sure about this one.