Simplify code by relying on newer Kokkos versions.

[bangerth]

My understanding from the cmake scripts is that we require at least Kokkos 3.7. If this is correct, we could simplify the following code that to me looks like it is also supporting versions of Kokkos before 3.6:

#ifdef DEBUG
#  if KOKKOS_VERSION >= 30600
#    ifdef DEAL_II_HAVE_BUILTIN_EXPECT
#      define Assert(cond, exc)                                                \
        do                                                                     \
          {                                                                    \
            KOKKOS_IF_ON_HOST(({                                               \
              if (__builtin_expect(!(cond), false))                            \
                ::dealii::deal_II_exceptions::internals::issue_error_noreturn( \
                  ::dealii::deal_II_exceptions::internals::ExceptionHandling:: \
                    abort_or_throw_on_exception,                               \
                  __FILE__,                                                    \
                  __LINE__,                                                    \
                  __PRETTY_FUNCTION__,                                         \
                  #cond,                                                       \
                  #exc,                                                        \
                  exc);                                                        \
            }))                                                                \
            KOKKOS_IF_ON_DEVICE(({                                             \
              if (!(cond))                                                     \
                Kokkos::abort(#cond);                                          \
            }))                                                                \
          }                                                                    \
        while (false)
#    else /*ifdef DEAL_II_HAVE_BUILTIN_EXPECT*/
#      define Assert(cond, exc)                                                \
        do                                                                     \
          {                                                                    \
            KOKKOS_IF_ON_HOST(({                                               \
              if (!(cond))                                                     \
                ::dealii::deal_II_exceptions::internals::issue_error_noreturn( \
                  ::dealii::deal_II_exceptions::internals::ExceptionHandling:: \
                    abort_or_throw_on_exception,                               \
                  __FILE__,                                                    \
                  __LINE__,                                                    \
                  __PRETTY_FUNCTION__,                                         \
                  #cond,                                                       \
                  #exc,                                                        \
                  exc);                                                        \
            }))                                                                \
            KOKKOS_IF_ON_DEVICE(({                                             \
              if (!(cond))                                                     \
                Kokkos::abort(#cond);                                          \
            }))                                                                \
          }                                                                    \
        while (false)
#    endif /*ifdef DEAL_II_HAVE_BUILTIN_EXPECT*/
#  else    /*if KOKKOS_VERSION >= 30600*/
#    ifdef KOKKOS_ACTIVE_EXECUTION_MEMORY_SPACE_HOST
#      ifdef DEAL_II_HAVE_BUILTIN_EXPECT
#        define Assert(cond, exc)                                              \
          do                                                                   \
            {                                                                  \
              if (__builtin_expect(!(cond), false))                            \
                ::dealii::deal_II_exceptions::internals::issue_error_noreturn( \
                  ::dealii::deal_II_exceptions::internals::ExceptionHandling:: \
                    abort_or_throw_on_exception,                               \
                  __FILE__,                                                    \
                  __LINE__,                                                    \
                  __PRETTY_FUNCTION__,                                         \
                  #cond,                                                       \
                  #exc,                                                        \
                  exc);                                                        \
            }                                                                  \
          while (false)
#      else /*ifdef DEAL_II_HAVE_BUILTIN_EXPECT*/
#        define Assert(cond, exc)                                              \
          do                                                                   \
            {                                                                  \
              if (!(cond))                                                     \
                ::dealii::deal_II_exceptions::internals::issue_error_noreturn( \
                  ::dealii::deal_II_exceptions::internals::ExceptionHandling:: \
                    abort_or_throw_on_exception,                               \
                  __FILE__,                                                    \
                  __LINE__,                                                    \
                  __PRETTY_FUNCTION__,                                         \
                  #cond,                                                       \
                  #exc,                                                        \
                  exc);                                                        \
            }                                                                  \
          while (false)
#      endif /*ifdef DEAL_II_HAVE_BUILTIN_EXPECT*/
#    else    /*#ifdef KOKKOS_ACTIVE_EXECUTION_MEMORY_SPACE_HOST*/
#      define Assert(cond, exc)     \
        do                          \
          {                         \
            if (!(cond))            \
              Kokkos::abort(#cond); \
          }                         \
        while (false)
#    endif /*ifdef KOKKOS_ACTIVE_EXECUTION_MEMORY_SPACE_HOST*/
#  endif   /*KOKKOS_ACTIVE_EXECUTION_MEMORY_SPACE_HOST*/
#else      /*ifdef DEBUG*/
#  define Assert(cond, exc) \
    do                      \
      {                     \
      }                     \
    while (false)
#endif /*ifdef DEBUG*/

[bangerth]

To be clear, there are plenty of other places that could also be simplified:

> grep -r KOKKOS_VERSION include/ source/ examples/ tests/
include/deal.II/base/utilities.h:#  if KOKKOS_VERSION >= 30600
include/deal.II/base/tensor.h:#  if KOKKOS_VERSION >= 30600
include/deal.II/base/memory_space_data.h:#if KOKKOS_VERSION < 40000
include/deal.II/base/memory_space_data.h:#  if KOKKOS_VERSION < 40000
include/deal.II/base/exceptions.h:#if KOKKOS_VERSION >= 40200
include/deal.II/base/exceptions.h:#  if KOKKOS_VERSION >= 30600
include/deal.II/base/exceptions.h:#  else    /*if KOKKOS_VERSION >= 30600*/
include/deal.II/lac/vector_operations_internal.h:#if KOKKOS_VERSION < 30400
include/deal.II/lac/vector_operations_internal.h:#elif KOKKOS_VERSION < 30700
include/deal.II/lac/vector_operations_internal.h:#if KOKKOS_VERSION < 30400
include/deal.II/lac/vector_operations_internal.h:#elif KOKKOS_VERSION < 30700
include/deal.II/lac/la_parallel_vector.templates.h:#if KOKKOS_VERSION < 30400
include/deal.II/lac/la_parallel_vector.templates.h:#elif KOKKOS_VERSION < 30700
include/deal.II/lac/la_parallel_vector.templates.h:#    if KOKKOS_VERSION < 40000
include/deal.II/lac/la_parallel_vector.templates.h:#    if KOKKOS_VERSION < 40000
include/deal.II/matrix_free/cuda_matrix_free.templates.h:#if KOKKOS_VERSION >= 30600
include/deal.II/matrix_free/cuda_matrix_free.templates.h:#if KOKKOS_VERSION >= 20900
include/deal.II/matrix_free/cuda_matrix_free.templates.h:#if KOKKOS_VERSION >= 20900
include/deal.II/matrix_free/cuda_matrix_free.templates.h:#if KOKKOS_VERSION >= 20900
include/deal.II/matrix_free/cuda_matrix_free.templates.h:#if KOKKOS_VERSION >= 20900
include/deal.II/matrix_free/cuda_matrix_free.templates.h:#if KOKKOS_VERSION >= 20900
include/deal.II/matrix_free/cuda_matrix_free.templates.h:#if KOKKOS_VERSION >= 20900
include/deal.II/matrix_free/cuda_matrix_free.templates.h:#if KOKKOS_VERSION >= 20900
include/deal.II/matrix_free/cuda_tensor_product_kernels.h:#if KOKKOS_VERSION >= 40000
include/deal.II/matrix_free/cuda_tensor_product_kernels.h:#if KOKKOS_VERSION >= 40000
source/base/kokkos.cc:#if KOKKOS_VERSION >= 30700
source/base/kokkos.cc:#if KOKKOS_VERSION >= 30700
source/base/mpi.cc:#if KOKKOS_VERSION >= 30700

[masterleinad]

The problem is that we support Trilinos versions that carry older Kokkos versions than 3.7.

[bangerth]

Oh. I had looked into cmake/modules/FindDEAL_II_KOKKOS.cmake where it says

if(DEAL_II_TRILINOS_WITH_KOKKOS OR DEAL_II_PETSC_WITH_KOKKOS)
  # Let ArborX know that we have found Kokkos
  set(Kokkos_FOUND ON)
  # Let deal.II know that we have found Kokkos
  set(KOKKOS_FOUND ON)
else()
  # silence a warning when including FindKOKKOS.cmake
  set(CMAKE_CXX_EXTENSIONS OFF)
  find_package(Kokkos 3.7.0 QUIET
    HINTS ${KOKKOS_DIR} ${Kokkos_DIR} $ENV{Kokkos_DIR}
    )

from which I had assumed that 3.7 is the earliest supported version.

What is the earliest supported version?

[masterleinad]

What is the earliest supported version?

https://www.dealii.org/current/external-libs/trilinos.html says we require Trilinos 12.14.1 if Kokkos is enabled in Trilinos. That version (released almost 5 years ago) bundles Kokkos 2.7.00 as far as I can tell (trilinos/Trilinos@626e32a).

[bangerth]

Ugh. Well, it was a nice idea :-)