Function npy_atry_collapse

numpy/core/src/npysort/timsort.cpp:2599–2658

}

static int
npy_atry_collapse(char *arr, npy_intp *tosort, run *stack, npy_intp *stack_ptr,
                  buffer_intp *buffer, size_t len, PyArray_CompareFunc *cmp,
                  PyArrayObject *py_arr)
{
    int ret;
    npy_intp A, B, C, top;
    top = *stack_ptr;

    while (1 < top) {
        B = stack[top - 2].l;
        C = stack[top - 1].l;

        if ((2 < top && stack[top - 3].l <= B + C) ||
            (3 < top && stack[top - 4].l <= stack[top - 3].l + B)) {
            A = stack[top - 3].l;

            if (A <= C) {
                ret = npy_amerge_at(arr, tosort, stack, top - 3, buffer, len,
                                    cmp, py_arr);

                if (NPY_UNLIKELY(ret < 0)) {
                    return ret;
                }

                stack[top - 3].l += B;
                stack[top - 2] = stack[top - 1];
                --top;
            }
            else {
                ret = npy_amerge_at(arr, tosort, stack, top - 2, buffer, len,
                                    cmp, py_arr);

                if (NPY_UNLIKELY(ret < 0)) {
                    return ret;
                }

                stack[top - 2].l += C;
                --top;
            }
        }
        else if (1 < top && B <= C) {
            ret = npy_amerge_at(arr, tosort, stack, top - 2, buffer, len, cmp,
                                py_arr);

            if (NPY_UNLIKELY(ret < 0)) {
                return ret;
            }

            stack[top - 2].l += C;
            --top;
        }
        else {
            break;
        }
    }

    *stack_ptr = top;