struct pivot_entry
{
    uint32_t nCnt;
    double fSum;
    double fPart;
    std::unordered_map<double, std::wstring> mStrings;
};
typedef std::unordered_map<std::wstring, std::unordered_map<std::wstring, std::unordered_map<std::wstring, std::unordered_map<std::wstring, pivot_entry>>>> pivot_map;

// look for Fld1
auto itFld1 = pm->find(pwszFld1);
if (itFld1 != pm->end())
{
    // look for Fld2
    auto itFld2 = itFld1->second.find(pwszFld2);
    if (itFld2 != itFld1->second.end())
    {
        // look for Fld3
        auto itFld3 = itFld2->second.find(pwszFld3);
        if (itFld3 != itFld2->second.end())
        {
            // look for Fld4
            auto itFld4 = itFld3->second.find(pwszFld4);
            if (itFld4 != itFld3->second.end())
            {
                // pivot_entry already exists - just update it
            }
            else
            {
                // add new pivot_entry from Fld4
            }
        }
        else
        {
            // add new pivot_entry from Fld3
        }
    }
    else
    {
        // add new pivot_enrty from Fld2
    }
}
else
{
    // add new pivot_entry from Fld1
    pm->emplace(pwszFld1, std::unordered_map<pwszFld2, std::unordered_map<pwszFld3, std::unordered_map<pwszFld4, >>>());
}

A>// look for Fld1
...
A>else
A>{
A>    // add new pivot_entry from Fld1
    pm->>emplace(pwszFld1, std::unordered_map<pwszFld2, std::unordered_map<pwszFld3, std::unordered_map<pwszFld4, >>>());
A>}
A>

(*pm)[pwszFld1][pwszFld2][pwszFld3][pwszFld4] = new_pivot_entry; // update with replace

auto& accumulator = (*pm)[pwszFld1][pwszFld2][pwszFld3][pwszFld4]; // это либо существующий аккумулятор, либо только что созданный. Но дальнейший код в любом случае одинаков

accumulator.counter_1 += update.counter_1;
accumulator.sum_2     += update.sum_2;
итд

std::unordered_map< std::tuple< std::wstring, std::wstring, std::wstring, std::wstring>, pivot_entry > pivot_map;

pivot_map[{"a", "b", "c", "d"}] = ...

using pivot_map_key = std::tuple<std::wstring, std::wstring, std::wstring, std::wstring>;
using pivot_map = std::unordered_map<pivot_map_key, pivot_entry>;

    const auto [it, inserted] = pm->emplace(pivot_map_key{"one", "two", "three", "four"}, pivot_entry{});
    auto& [key, pivot] = *it;
    if (inserted)
    {
        // Process insertion
    }
    else
    {
        // Update existing entry
    }

    pivot_entry& pivot = {*pm}[{"one", "two", "three", "four"}];
    // Update new or existing entry...

R>using pivot_map_key = std::tuple<std::wstring, std::wstring, std::wstring, std::wstring>;
R>using pivot_map = std::unordered_map<pivot_map_key, pivot_entry>;
R>

R>    pivot_entry& pivot = {*pm}[{"one", "two", "three", "four"}];
R>    // Update new or existing entry...
R>

struct pivot_entry
{
    uint32_t nCnt;
    double fSum;
    double fPart;
};
using pivot_key = std::tuple<std::wstring, std::wstring, std::wstring, std::wstring>;
using pivot_map = std::unordered_map<pivot_key, pivot_entry>;

Error C2280 'std::_Uhash_compare<_Kty,_Hasher,_Keyeq>::_Uhash_compare(const std::_Uhash_compare<_Kty,_Hasher,_Keyeq> &)': attempting to reference a deleted function

A>struct pivot_entry
A>{
A>    uint32_t nCnt;
A>    double fSum;
A>    double fPart;
A>};
A>using pivot_key = std::tuple<std::wstring, std::wstring, std::wstring, std::wstring>;
A>using pivot_map = std::unordered_map<pivot_key, pivot_entry>;
A>

using pivot_map_key = std::tuple<std::wstring, std::wstring, std::wstring, std::wstring>;

struct pivot_map_hash
{
    size_t operator()(const pivot_map_key& key) const
    {
        using str_hash = std::hash<std::wstring>;
        return
            str_hash()(std::get<0>(key)) ^
            (str_hash()(std::get<1>(key)) << 1) ^
            (str_hash()(std::get<2>(key)) << 2) ^
            (str_hash()(std::get<3>(key)) << 3);
    }
};

using pivot_map = std::unordered_map<pivot_map_key, pivot_entry, pivot_map_hash>;

pivot_entry& pivot = (*pm)[{"one", "two", "three", "four"}];

C>std::unordered_map< std::tuple< std::wstring, std::wstring, std::wstring, std::wstring>, pivot_entry > pivot_map;

C>pivot_map[{"a", "b", "c", "d"}] = ... 
C>

typedef std::unordered_map<std::wstring, std::unordered_map<std::wstring, std::unordered_map<std::wstring, std::unordered_map<std::wstring, pivot_entry>>>> pivot_map;

    const string a5{"aaaaa"};

    unordered_set<string> cc;


    cc.emplace(a5);
    cc.emplace("aaaaa");
    cc.emplace(begin(a5), end(a5));
    cc.emplace(5, 'a');

map<U, V> sm;
sm.emplace(4, 5);

struct U {
    U(int);
    U(const U&) = delete; // oops
    friend bool operator==(const U&, const U&);
};

struct U {
W>>>    U(int);
W>>>    U(const U&) = delete; // oops
W>>>    friend bool operator==(const U&, const U&);
W>>>};
W>>>

namespace std {
    template<>
    struct hash<S> {
        size_t operator()(const S& s) const {
            return reinterpret_cast<uintptr_t>(this);
        }
    };
}

        size_t operator()(const S& s) const {
            return reinterpret_cast<uintptr_t>(&s);
        }

        size_t operator()(const S& s) const {
            return 12345678;
        }

key_t key(param1);
node_t node(param1, param2);