Program Listing for File ApplyCZ.hpp

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// Copyright 2018-2023 Xanadu Quantum Technologies Inc.

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at

//     http://www.apache.org/licenses/LICENSE-2.0

// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#pragma once
#include "AVXConceptType.hpp"
#include "AVXUtil.hpp"
#include "BitUtil.hpp"
#include "Util.hpp"

#include <complex>

namespace Pennylane::LightningQubit::Gates::AVXCommon {
template <typename PrecisionT, std::size_t packed_size> struct ApplyCZ {
    using Precision = PrecisionT;
    using PrecisionAVXConcept = AVXConceptType<PrecisionT, packed_size>;

    constexpr static std::size_t packed_size_ = packed_size;
    constexpr static bool symmetric = true;

    template <size_t rev_wire0, std::size_t rev_wire1>
    static void applyInternalInternal(std::complex<PrecisionT> *arr,
                                      std::size_t num_qubits,
                                      [[maybe_unused]] bool inverse) {
        const auto parity = toParity<PrecisionT, packed_size>([](size_t idx) {
            return ((idx >> rev_wire0) & 1U) & ((idx >> rev_wire1) & 1U);
        });

        PL_LOOP_PARALLEL(1)
        for (size_t n = 0; n < exp2(num_qubits); n += packed_size / 2) {
            const auto v = PrecisionAVXConcept::load(arr + n);
            PrecisionAVXConcept::store(arr + n, v * parity);
        }
    }

    template <size_t min_rev_wire>
    static void applyInternalExternal(std::complex<PrecisionT> *arr,
                                      std::size_t num_qubits,
                                      std::size_t max_rev_wire,
                                      [[maybe_unused]] bool inverse) {
        const std::size_t max_rev_wire_shift =
            (static_cast<std::size_t>(1U) << max_rev_wire);
        const std::size_t max_wire_parity = fillTrailingOnes(max_rev_wire);
        const std::size_t max_wire_parity_inv =
            fillLeadingOnes(max_rev_wire + 1);

        const auto parity =
            internalParity<PrecisionT, packed_size>(min_rev_wire);
        PL_LOOP_PARALLEL(1)
        for (size_t k = 0; k < exp2(num_qubits - 1); k += packed_size / 2) {
            const std::size_t i0 =
                ((k << 1U) & max_wire_parity_inv) | (max_wire_parity & k);
            const std::size_t i1 = i0 | max_rev_wire_shift;

            const auto v1 = PrecisionAVXConcept::load(arr + i1);

            PrecisionAVXConcept::store(arr + i1, v1 * parity);
        }
    }

    static void applyExternalExternal(std::complex<PrecisionT> *arr,
                                      const std::size_t num_qubits,
                                      const std::size_t rev_wire0,
                                      const std::size_t rev_wire1,
                                      [[maybe_unused]] bool inverse) {
        const std::size_t rev_wire0_shift = static_cast<std::size_t>(1U)
                                            << rev_wire0;
        const std::size_t rev_wire1_shift = static_cast<std::size_t>(1U)
                                            << rev_wire1;

        const std::size_t rev_wire_min = std::min(rev_wire0, rev_wire1);
        const std::size_t rev_wire_max = std::max(rev_wire0, rev_wire1);

        const std::size_t parity_low = fillTrailingOnes(rev_wire_min);
        const std::size_t parity_high = fillLeadingOnes(rev_wire_max + 1);
        const std::size_t parity_middle =
            fillLeadingOnes(rev_wire_min + 1) & fillTrailingOnes(rev_wire_max);

        PL_LOOP_PARALLEL(1)
        for (size_t k = 0; k < exp2(num_qubits - 2); k += packed_size / 2) {
            const std::size_t i00 = ((k << 2U) & parity_high) |
                                    ((k << 1U) & parity_middle) |
                                    (k & parity_low);
            const std::size_t i11 = i00 | rev_wire0_shift | rev_wire1_shift;

            const auto v = PrecisionAVXConcept::load(arr + i11); // 11
            PrecisionAVXConcept::store(arr + i11, -1.0 * v);
        }
    }
};
} // namespace Pennylane::LightningQubit::Gates::AVXCommon

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