Check if entire vector is zero

Question

How could I check if every single element in a vector is zero without looping through them?

Current I have (In semi-MEW form): What this attempts to do is check if all three values of the final vector (its three dimensional... year.) is all zeros, (At the origin), or if it equals any previous vector on all three values.

        siteVisited = false; counter = 0;  
        while (counter < (walkHist.back().size()-1))
        {
            tdof = 1;
            while (tdof <= dimensions)
            {
                if (walkHist.back().back().at(tdof-1) == 0)
                {
                    siteVisited = true;
                }
                else
                {
                    siteVisited = false;
                    break;
                }
                tdof++;
            }
            if (siteVisited)
            {
                goto visited;
            }

            tdof = 1;
            while (tdof <= dimensions)
            {
                if (walkHist.back().back().at(tdof-1) == walkHist.back().at(counter).at(tdof-1))
                {
                    siteVisited = true;
                }
                else
                {
                    siteVisited = false;
                    break;
                }
                tdof++;
            }
            if (siteVisited)
            {
                                visited:
                ...
            }
            counter++;
        }

Answer 1

It depends on what you mean by looping, but this would work:

bool zeros = std::all_of(v.begin(), v.end(), [](int i) { return i==0; });

Answer 2

The reason for the check is important to know. If a zeroed array is important, and is checked regularly, it would be worth sub-classing vector to set a flag whenever a value is added or changed. This would add overhead to all adds, removes and modified, but would make the "is everything zero" test quick.

If your arrays are very often zeroed, it might then be worth writing your own sparse array class (probably based on map). When a non-zero item is added, or an element is changed to non-zero it is entered into the map. When changed to 0 it is removed. Now you know if all the elements are zero because the map will be empty. This will also have the benefit of using much less memory.

However, if the check for a zeroed array is comparatively rare, then any loop which breaks on non-zero will work well. It does, however, mean that the slowest check will be on all zero, which is worth keeping in mind.