message: removed some redundant code and unused variables
diff: @@ -165,7 +165,7 @@ using are_span_compatible = are_span_compatible_impl<false, Args...>;
  template <typename ValueType, size_type N, size_type current, typename... Dims>
  constexpr GKO_ATTRIBUTES
  std::enable_if_t<(current == N), std::array<ValueType, N>>
  - to_array_impl(const dim<N> &size, Dims &&... dims)
  + to_array_impl(const dim<N> &, Dims &&... dims)
  {
  static_assert(sizeof...(Dims) == N,
  "Number of arguments must match dimensionality!");
  @@ -674,7 +674,6 @@ template <typename ValueType, size_type total_dim>
  struct index_helper_s<ValueType, total_dim, total_dim> {
  static_assert(total_dim >= 2, "Dimensionality must be >= 2");
  - // static constexpr size_type current_iter = total_dim;
  static constexpr size_type dim_idx{total_dim - 1};
  template <typename FirstType, typename... Indices>
  @@ -682,7 +681,7 @@ struct index_helper_s<ValueType, total_dim, total_dim> {
  compute(const std::array<ValueType, total_dim> &size,
  const std::array<ValueType, (total_dim > 1 ? total_dim - 1 : 0)>
  &stride,
  - FirstType first, Indices &&... idxs)
  + FirstType first, Indices &&...)
  {
  return GKO_ASSERT(first < size[total_dim - 1]),
  first * stride[dim_idx - 1];
  @@ -704,20 +703,6 @@ constexpr GKO_ATTRIBUTES ValueType compute_index(
  }
  -template <size_type iter, typename ValueType, size_type N>
  -constexpr GKO_ATTRIBUTES std::enable_if_t<iter == N, ValueType>
  -mult_dim_upwards_impl(const std::array<ValueType, N> &size)
  -{
  - return 1;
  -}
  -
  -template <size_type iter, typename ValueType, size_type N>
  -constexpr GKO_ATTRIBUTES std::enable_if_t<(iter < N), ValueType>
  -mult_dim_upwards_impl(const std::array<ValueType, N> &size)
  -{
  - return size[iter] * mult_dim_upwards_impl<iter + 1>(size);
  -}
  -
  template <size_type iter = 1, typename ValueType, size_type N, typename... Args>
  constexpr GKO_ATTRIBUTES
  std::enable_if_t<(iter == N - 1) && (iter == sizeof...(Args) + 1),
  @@ -735,7 +720,8 @@ constexpr GKO_ATTRIBUTES std::enable_if_t<(iter < N - 1 || iter == N) &&
  default_stride_array_impl(const std::array<ValueType, N> &size, Args &&... args)
  {
  return default_stride_array_impl<iter + 1>(
  - size, std::forward<Args>(args)..., mult_dim_upwards_impl<iter>(size));
  + size, std::forward<Args>(args)...,
  + detail::mult_dim_upwards_impl<iter>(size));
  }
  template <typename ValueType, size_type dimensions>
  