[Proposal] Convert Templated XXXFor Structs to Objects about qsim HOT 6 CLOSED

Some context on the qsim side: this should only affect the *for.h, simulator_*.h, and statespace_*.h files. TFQ calls the methods provided by simulator and statespace, so the new For object could be passed in from there.

This is in the simulation "hot path", but by passing reference objects I think we can avoid any significant performance impact.

from qsim.

I think this is a good proposal. I'll do this in a slightly different way like this:

template <typename For>
class SimulatorAVX {
...

  template <typename... Args>
  SimulatorAVX(unsigned num_qubits, Args&&... args)
      : for_(args...), num_qubits_(num_qubits) {}

...

  For for_;

...

};

Instead of passing a For object to every function, I keep the classes templated and add a (lightweight) For object to them. This requires only minimal changes to statespace*.h and to simulator*.h and basically no changes to the existing client code and tests.

from qsim.

Ok, just to clarify with this new way of doing things can I still do something like this ?

auto my_for = tfq::TFQFor(tfOpKernelContext->get_available_cpu_workers())
auto qsim_simulator = SimulatorAVX<tfq::TFQFor>(num_qubits, ... , my_for);  // my_far passed in as a const TFQFor& ?

and expect things to work ?

from qsim.

Yes, it is expected to work if tfq::TFQFor has a copy constructor (user-defined or implicit). One doesn't have to define my_for. The following will also work:

qsim_simulator = SimulatorAVX<tfq::TFQFor>(num_qubits, tfOpKernelContext->get_available_cpu_workers());

from qsim.

Ok great.

I’ll do this in a slightly different way ...

When could we expect this to be a part of qsim with a new GitHub release ?

from qsim.

Hopefully, it will be in the repository in less than a week.

from qsim.