Function das_partial_sort_r

include/daScript/simulate/das_qsort_r.h:771–789

// sorted output. O(M log N). Matches std::partial_sort.
template <typename Compare>
inline void das_partial_sort_r(void *base, size_t nel, size_t n, size_t width, Compare cmp)
{
    if (nel <= 1 || n == 0) return;
    if (n > nel) n = nel;
    unsigned char *data = (unsigned char *)base;
    das_make_heap_r(data, n, width, cmp);
    for (size_t i = n; i < nel; i++) {
        unsigned char *xi = data + i * width;
        if (cmp(xi, data)) {           // a[i] < heap top (current Nth-smallest)
            byte_swap(data, xi, width);// displace top to position i (outside heap; never revisited)
            das_sift_down_r(data, 0, n, width, cmp);
        }
    }
    // Drain: pop max repeatedly into positions n-1, n-2, ...
    for (size_t len = n; len > 1; len--) {
        byte_swap(data, data + (len - 1) * width, width);
        das_sift_down_r(data, 0, len - 1, width, cmp);
    }
}

// ============================================================================
// Stable sort — adaptive natural-run merge (timsort-lite, no galloping).