bempp.api.utils.pool.create_device_pool uses functions from cl_helpers, which does not exist.

[boomboompsh]

It looks like cl_helpers was removed when the numba kernels were added and was then never reinstated. I'm not sure what this function is supposed to do, but it's commented out in the maxwell dielectric sphere example.
a0ee507#diff-5ac16593fe83707205b8bc070160f4ccb59f21b5fbcdcc65f516fde340776447 was the last commit with cl_helpers working.

[tbetcke]

Thanks for noting this. This was indeed supposed to be removed. We added very experimental multi-GPU support earlier on. But it never worked very well with Nvidia cards due to some issues in Nvidia's OpenCL implementation with multiple GPUs. We had a very hacky work-around. But it was too messy to keep in.