Making terrain list GPU aware

Source/SourceTerms/ERF_TerrainDrag.cpp

@@ -38,7 +38,22 @@ TerrainDrag::define_terrain_blank_field(
   m_terrain_blank.reset();
   m_terrain_blank = std::make_unique<MultiFab>(ba, dm, 1, 1);
   m_terrain_blank->setVal(0.);
-
+  const auto xterrain_size = m_x_terrain.size();
+  amrex::Gpu::DeviceVector<amrex::Real> d_xterrain(xterrain_size);
+  amrex::Gpu::DeviceVector<amrex::Real> d_yterrain(xterrain_size);
+  amrex::Gpu::DeviceVector<amrex::Real> d_zterrain(xterrain_size);
+  amrex::Gpu::copy(
+        amrex::Gpu::hostToDevice, m_x_terrain.begin(), m_x_terrain.end(),
+        d_xterrain.begin());
+  amrex::Gpu::copy(
+        amrex::Gpu::hostToDevice, m_y_terrain.begin(), m_y_terrain.end(),
+        d_yterrain.begin());
+  amrex::Gpu::copy(
+        amrex::Gpu::hostToDevice, m_height_terrain.begin(), m_height_terrain.end(),
+        d_zterrain.begin());
+    const auto* xterrain_ptr = d_xterrain.data();
+    const auto* yterrain_ptr = d_yterrain.data();
+    const auto* zterrain_ptr = d_zterrain.data();  
   // Set the terrain blank data
   for (MFIter mfi(*m_terrain_blank); mfi.isValid(); ++mfi) {
     Box gtbx = mfi.growntilebox();
@@ -47,10 +62,10 @@ TerrainDrag::define_terrain_blank_field(
       (z_phys_nd) ? z_phys_nd->const_array(mfi) : Array4<const Real>{};
     ParallelFor(gtbx, [=] AMREX_GPU_DEVICE(int i, int j, int k) noexcept {
       // Loop over terrain points
-      for (unsigned ii = 0; ii < m_x_terrain.size(); ++ii) {
-        Real ht = m_height_terrain[ii];
-        Real xt = m_x_terrain[ii];
-        Real yt = m_y_terrain[ii];
+      for (unsigned ii = 0; ii < xterrain_size; ++ii) {
+        Real ht = zterrain_ptr[ii];
+        Real xt = xterrain_ptr[ii];
+        Real yt = yterrain_ptr[ii];
         // Physical positions of cell-centers
         const Real x = prob_lo[0] + (i + 0.5) * dx[0];
         const Real y = prob_lo[1] + (j + 0.5) * dx[1];