Function createDiagMatr

quest/src/api/matrices.cpp:248–274

extern "C" DiagMatr createDiagMatr(int numQubits) {
    validate_envIsInit(__func__);
    validate_newDiagMatrParams(numQubits, __func__);

    // validation ensures this never overflows
    qindex numElems = powerOf2(numQubits);

    // prepare output DiagMatr (avoiding C++20 designated initialiser)
    DiagMatr out;
    out.numQubits = numQubits,
    out.numElems = numElems,

    // attempt to allocate (uninitialised) flags in the heap so that struct copies are mutable
    out.isApproxUnitary       = util_allocEpsilonSensitiveHeapFlag(); // nullptr if failed
    out.isApproxHermitian     = util_allocEpsilonSensitiveHeapFlag();
    out.isApproxNonZero       = util_allocEpsilonSensitiveHeapFlag();
    out.isStrictlyNonNegative = cpu_allocHeapFlag(); // nullptr if failed
    out.wasGpuSynced          = cpu_allocHeapFlag();

    // attempt to allocate 1D memory (nullptr if failed or not allocated)
    out.cpuElems = cpu_allocArray(numElems);
    out.gpuElems = (getQuESTEnv().isGpuAccelerated)? gpu_allocArray(numElems) : nullptr;

    validateMatrixAllocs(out, __func__);
    setInitialHeapFlags(out);
    return out;
}


FullStateDiagMatr validateAndCreateCustomFullStateDiagMatr(int numQubits, int useDistrib, int useGpuAccel, int useMultithread, const char* caller) {