ParticleTile: More SoA Updates (#3305)

## Summary

More updates to `ParticleTile` and simplifications for pure SoA support.

## Additional background

Isolated from #3290 and author credited to @AlexanderSinn.

## Checklist

The proposed changes:
- [ ] fix a bug or incorrect behavior in AMReX
- [ ] add new capabilities to AMReX
- [ ] changes answers in the test suite to more than roundoff level
- [ ] are likely to significantly affect the results of downstream AMReX
users
- [ ] include documentation in the code and/or rst files, if appropriate

Co-authored-by: Alexander Sinn <[email protected]>

Author: ax3l

Src/Particle/AMReX_ParticleTile.H

@@ -109,25 +109,13 @@ struct ParticleTileData
     }
 
     AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
-    auto* rdata (const int attribute_index)
+    auto * rdata (const int attribute_index) const
     {
         return this->m_rdata[attribute_index];
     }
 
     AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
-    auto const * rdata (const int attribute_index) const
-    {
-        return this->m_rdata[attribute_index];
-    }
-
-    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
-    auto* idata (const int attribute_index)
-    {
-        return this->m_idata[attribute_index];
-    }
-
-    AMREX_GPU_HOST_DEVICE AMREX_FORCE_INLINE
-    auto const * idata (const int attribute_index) const
+    auto * idata (const int attribute_index) const
     {
         return this->m_idata[attribute_index];
     }
@@ -746,11 +734,7 @@ struct ParticleTile
     SoA&       GetStructOfArrays ()       { return m_soa_tile; }
     const SoA& GetStructOfArrays () const { return m_soa_tile; }
 
-    template <typename T = ParticleType, typename std::enable_if<!T::is_soa_particle, int>::type = 0>
-    bool empty () const { return m_aos_tile.empty(); }
-
-    template <typename T = ParticleType, typename std::enable_if<T::is_soa_particle, int>::type = 0>
-    bool empty () const { return m_soa_tile.empty(); }
+    bool empty () const { return size() == 0; }
 
     /**
     * \brief Returns the total number of particles (real and neighbor)
@@ -817,7 +801,9 @@ struct ParticleTile
 
     void resize (std::size_t count)
     {
-        m_aos_tile.resize(count);
+        if constexpr (!ParticleType::is_soa_particle) {
+            m_aos_tile.resize(count);
+        }
         m_soa_tile.resize(count);
     }
 
@@ -969,7 +955,9 @@ struct ParticleTile
 
     void shrink_to_fit ()
     {
-        m_aos_tile().shrink_to_fit();
+        if constexpr (!ParticleType::is_soa_particle) {
+            m_aos_tile().shrink_to_fit();
+        }
         for (int j = 0; j < NumRealComps(); ++j)
         {
             auto& rdata = GetStructOfArrays().GetRealData(j);
@@ -986,7 +974,9 @@ struct ParticleTile
     Long capacity () const
     {
         Long nbytes = 0;
-        nbytes += m_aos_tile().capacity() * sizeof(ParticleType);
+        if constexpr (!ParticleType::is_soa_particle) {
+            nbytes += m_aos_tile().capacity() * sizeof(ParticleType);
+        }
         for (int j = 0; j < NumRealComps(); ++j)
         {
             auto& rdata = GetStructOfArrays().GetRealData(j);
@@ -1003,7 +993,9 @@ struct ParticleTile
 
     void swap (ParticleTile<ParticleType, NArrayReal, NArrayInt, Allocator>& other)
     {
-        m_aos_tile().swap(other.GetArrayOfStructs()());
+        if constexpr (!ParticleType::is_soa_particle) {
+            m_aos_tile().swap(other.GetArrayOfStructs()());
+        }
         for (int j = 0; j < NumRealComps(); ++j)
         {
             auto& rdata = GetStructOfArrays().GetRealData(j);
@@ -1052,7 +1044,11 @@ struct ParticleTile
 #endif
 
         ParticleTileDataType ptd;
-        ptd.m_aos = m_aos_tile().dataPtr();
+        if constexpr (!ParticleType::is_soa_particle) {
+            ptd.m_aos = m_aos_tile().dataPtr();
+        } else {
+            ptd.m_aos = nullptr;
+        }
         if constexpr(NArrayReal > 0)
             for (int i = 0; i < NArrayReal; ++i)
                 ptd.m_rdata[i] = m_soa_tile.GetRealData(i).dataPtr();
@@ -1109,7 +1105,11 @@ struct ParticleTile
 #endif
 
         ConstParticleTileDataType ptd;
-        ptd.m_aos = m_aos_tile().dataPtr();
+        if constexpr (!ParticleType::is_soa_particle) {
+            ptd.m_aos = m_aos_tile().dataPtr();
+        } else {
+            ptd.m_aos = nullptr;
+        }
         if constexpr(NArrayReal > 0)
             for (int i = 0; i < NArrayReal; ++i)
                 ptd.m_rdata[i] = m_soa_tile.GetRealData(i).dataPtr();