Fastest way to sort a list of number and their index

Question

I have a question that could seem very basic, but it is in a context where \"every CPU tick counts\" (this is a part of a larger algorithm that will be used on supercomputers).<

Answer 1

struct SomeValue
{
    unsigned long long val;
    size_t index;
    bool operator<(const SomeValue& rhs)const
    { 
       return val < rhs.val;
    }
}

 #include 
 std::vector somevec;
 //fill it...
 std::sort(somevec.begin(),somevec.end());