Serialize kokkos views

[lifflander]

This is being implemented by @mperrinel with help from @nmm0

Please track progress on this in this issue.

[lifflander]

Test are now passing for Kokkos::View<T,Args...> and Kokkos::Experimental::DynamicView<T,Args...> for a wide range of T. See checkpoint/tests/unit/kokkos-serialize.cc for the full set of tests.

The unit tests pass with three layouts: LayoutLeft, LayoutRight, and LayoutStride.

For each of these three layouts, these View types (T) are tested in 1-D, 2-D, and 3-D:

using Test1DTypes = std::tuple<
  int      *, int      [1], int      [4],
  double   *, double   [1], double   [4],
  float    *, float    [1], float    [4],
  int32_t  *, int32_t  [1], int32_t  [4],
  int64_t  *, int64_t  [1], int64_t  [4],
  unsigned *, unsigned [1], unsigned [4],
  long     *, long     [1], long     [4],
  long long*, long long[1], long long[4]
>;

using Test2DTypes = std::tuple<
  int      **, int      *[1], int      *[4],
  double   **, double   *[1], double   *[4],
  float    **, float    *[1], float    *[4],
  int32_t  **, int32_t  *[1], int32_t  *[4],
  int64_t  **, int64_t  *[1], int64_t  *[4],
  unsigned **, unsigned *[1], unsigned *[4],
  long     **, long     *[1], long     *[4],
  long long**, long long*[1], long long*[4]
>;

using Test3DTypes = std::tuple<
  int      ***, int      **[1], int      **[9],
  double   ***, double   **[1], double   **[9],
  float    ***, float    **[1], float    **[9],
  int32_t  ***, int32_t  **[1], int32_t  **[9],
  int64_t  ***, int64_t  **[1], int64_t  **[9],
  unsigned ***, unsigned **[1], unsigned **[9],
  long     ***, long     **[1], long     **[9],
  long long***, long long**[1], long long**[9]
>;

The unit tests check deep equality between the views by accessing the data and comparing values before and after serialization.

The final integration test utilizes a class with multiple views, std::vector, and other data and checks for correctness by populating the data and asserting the data values are identical after serialization and deserialization.

struct BaseData { int a = 10; };
struct Data : BaseData {
  using Kokkos_ViewType1 = ::Kokkos::View<int*,     Kokkos::LayoutLeft>;
  using Kokkos_ViewType2 = ::Kokkos::View<double**, Kokkos::LayoutRight>;
  using Kokkos_ViewType3 = ::Kokkos::View<float***>;
  using Kokkos_ViewType4 = ::Kokkos::View<int*[2]>;
 
 //...

private:
  std::vector<int> vec = {};
  int val1 = 1, val2 = 2;
  Kokkos_ViewType1 v1;
  Kokkos_ViewType2 v2;
  Kokkos_ViewType3 v3;
  Kokkos_ViewType4 v4;
};