Function cpu_statevec_anyCtrlSwap_subC

quest/src/cpu/cpu_subroutines.cpp:346–375

template <int NumCtrls>
void cpu_statevec_anyCtrlSwap_subC(Qureg qureg, vector<int> ctrls, vector<int> ctrlStates, int targ, int targState) {

    assert_numCtrlsMatchesNumCtrlStatesAndTemplateParam(ctrls.size(), ctrlStates.size(), NumCtrls);

    // each control qubit halves the number of iterations, each of which modifies one of the two target qubit states
    qindex numIts = qureg.numAmpsPerNode / powerOf2(1 + ctrls.size());

    // received amplitudes may begin at an arbitrary offset in the buffer
    qindex offset = getBufferRecvInd();

    auto sortedQubits   = util_getSorted(ctrls, {targ});
    auto qubitStateMask = util_getBitMask(ctrls, ctrlStates, {targ}, {targState});
    
    // use template param to compile-time unroll loop in insertBits()
    SET_VAR_AT_COMPILE_TIME(int, numCtrlBits, NumCtrls, ctrls.size());
    int numQubitBits = numCtrlBits + 1;

    #pragma omp parallel for if(qureg.isMultithreaded)
    for (qindex n=0; n<numIts; n++) {

        // i = nth local index where ctrls and targ are in specified states
        qindex i = insertBitsWithMaskedValues(n, sortedQubits.data(), numQubitBits, qubitStateMask);
    
        // j = index of nth received amplitude from pair rank in buffer
        qindex j = n + offset;

        // unpack the continuous sub-buffer among the strided local amplitudes
        qureg.cpuAmps[i] = qureg.cpuCommBuffer[j];
    }
}


INSTANTIATE_FUNC_OPTIMISED_FOR_NUM_CTRLS( void, cpu_statevec_anyCtrlSwap_subA, (Qureg qureg, vector<int> ctrls, vector<int> ctrlStates, int targ1, int targ2) )