Function localiser_statevec_getAmp

quest/src/core/localiser.cpp:470–496

qcomp localiser_statevec_getAmp(Qureg qureg, qindex globalInd) {

    // this custom routine exists, in lieu of merely invoking
    // getAmps() below, because it avoids the superfluous rank
    // enumeration and is therefore locally faster; there
    // may be applications where this is desirable (maybe)

    // when qureg not distributed (although env may be), every
    // node returns their identical local amp
    if (!qureg.isDistributed) {
        qcomp amp;
        accel_statevec_getAmps_sub(&amp, qureg, globalInd, 1);
        return amp;
    }

    // otherwise one node contains the target amp
    qcomp amp = 0;
    int sender = util_getRankContainingIndex(qureg, globalInd);
    if (sender == qureg.rank) {
        qindex localInd = util_getLocalIndexOfGlobalIndex(qureg, globalInd);
        accel_statevec_getAmps_sub(&amp, qureg, localInd, 1);
    }

    // which it shares with all other nodes
    comm_broadcastAmp(sender, &amp);
    return amp;
}


void localiser_statevec_getAmps(qcomp* outAmps, Qureg qureg, qindex globalStartInd, qindex globalNumAmps) {