[idea] Theoretical speed estimation

[belltailjp]

As we not have a theoretical computational cost, if we have a theoretical specification of a device, we can estimate theoretical (upper-bound) of inference speed on the device.
It'd be nice if chainer_computational_cost can have a feature to receive a hardware profile and calculate layer-wise and total theoretical speed.

Problems

• Interface design
  • Embed inference time inside layer report?
    • Pros: implementation is the simplest
    • Cons: Need to specify only one hardware profile to Hook instance.
• Layer-specific accelerator
  • NVIDIA Volta has TensorCore, in V100 case convolution operation is 125TFLOPs, although other general arithmetics are 15TFLOPs.
  • If we use only one value as the hardware's theoretical performance, the estimated inference time is totally useless.