QCSimState.h

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#pragma once
#if defined(INCLUDED_BY_FACTORY)
#include "../Fusion/FusionState.h"
 
namespace Simulators::Private
{
class QCSimState : public FusionState
{
  public:
    explicit QCSimState(std::shared_ptr<ISimulator> immediate) : FusionState(std::move(immediate))
    {
    }
 
    unsigned GetGateFusionMaxQubits() const override
    {
        switch (GetSimulationType())
        {
        case SimulationType::kStatevector:
        case SimulationType::kDensityMatrix:
            return 3;
        case SimulationType::kMatrixProductState:
        case SimulationType::kMatrixProductOperator:
        case SimulationType::kTensorNetwork:
            return 2;
        default:
            return 0;
        }
    }
 
  protected:
    // Measured break-even of fused against native execution (geometric mean
    // over random, QAOA, QFT, quantum-volume and GHZ circuits). Below it the
    // state fits in cache, so fusing saves no memory passes and the dense
    // kernels cost more than the native gates they replace.
    size_t DefaultGateFusionMinQubits() const override
    {
        switch (GetSimulationType())
        {
        case SimulationType::kStatevector:
            return 11;
        case SimulationType::kDensityMatrix:
            return 5;
        default:
            return 0;
        }
    }
};
} // namespace Simulators::Private
#endif