Proposal to add iterative merge sort to benchmark

[furkansimsekli]

R4 failed to complete recursive merge sort for a given array that has 2048 integers in it. Iterative merge sort even completed its work until I switched tab to serial monitor to see the results.

At least one other algorithm also failed with 2048 int test: radix sort. We should find a way to solve this "scientifically". I mean some algorithms work but others dont, what are we gonna do? stop? I don't think so. I haven't tested with 4096 integers but I can sense that some of the algorithms will keep working even with 4096 integers. What I mean by scientific is that we need to find a way to label the failing algorithms. In this case we also need to adapt our visualization tool.

// 11. Iterative Merge Sort

void merge(int arr[], int left, int mid, int right) {
    int n1 = mid - left + 1;
    int n2 = right - mid;
    int L[n1], R[n2];

    for (int i = 0; i < n1; i++) L[i] = arr[left + i];
    for (int j = 0; j < n2; j++) R[j] = arr[mid + 1 + j];

    int i = 0, j = 0, k = left;
    while (i < n1 && j < n2) {
        if (L[i] <= R[j]) arr[k++] = L[i++];
        else arr[k++] = R[j++];
    }
    while (i < n1) arr[k++] = L[i++];
    while (j < n2) arr[k++] = R[j++];
}

void iterativeMergeSort(int arr[], int n) {
    for (int currSize = 1; currSize < n; currSize *= 2) {
        for (int leftStart = 0; leftStart < n - 1; leftStart += 2 * currSize) {
            int mid = leftStart + currSize - 1;
            int rightEnd = (leftStart + 2 * currSize - 1 < n - 1) ? (leftStart + 2 * currSize - 1) : (n - 1);
            if (mid < rightEnd) merge(arr, leftStart, mid, rightEnd);
        }
    }
}

[furkansimsekli]

We decided that we would do this in a new experiment called sort v2. I'm currently looking for other algorithms that worths including.