Function evaluate_ising

dwave/cloud/utils/qubo.py:48–75

Calculate the energy of a state given the Hamiltonian. Args: linear: Linear Hamiltonian terms. quad: Quadratic Hamiltonian terms. offset: Energy offset. state: Vector of spins describing the system state Returns: Energy of the state evaluated by the

(linear: Union[Mapping, Sequence],
                   quad: Mapping,
                   state: Sequence,
                   offset: float = 0
                   )

def evaluate_ising(linear: Union[Mapping, Sequence],
                   quad: Mapping,
                   state: Sequence,
                   offset: float = 0
                   ) -> float:
    """Calculate the energy of a state given the Hamiltonian.

    Args:
        linear: Linear Hamiltonian terms.
        quad: Quadratic Hamiltonian terms.
        offset: Energy offset.
        state: Vector of spins describing the system state

    Returns:
        Energy of the state evaluated by the given energy function.
    """

    # note: we avoid numpy import by tolist() check
    if hasattr(state, 'tolist') and callable(state.tolist):
        return evaluate_ising(linear, quad, state.tolist(), offset=offset)

    # Accumulate the linear and quadratic values
    energy = offset
    for index, value in uniform_iterator(linear):
        energy += state[index] * value
    for (index_a, index_b), value in quad.items():
        energy += value * state[index_a] * state[index_b]
    return energy


def active_qubits(linear: Union[Mapping, Sequence],