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Fuse boundary kernel
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streeve committed Jun 1, 2023
1 parent 8a168d6 commit c2ea6ea
Showing 1 changed file with 25 additions and 13 deletions.
38 changes: 25 additions & 13 deletions example/methods/finite_difference/finite_difference.cpp
Original file line number Diff line number Diff line change
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#include <Cajita.hpp>

// Apply boundary conditions. For simplicity of the code, rebuild the index
// spaces each step even though it's a fixed geometry. Apply all boundaries in
// one kernel for performance.
template <class ExecutionSpace, class LocalGridType, class ArrayType>
void updateBoundaries( ExecutionSpace exec_space, LocalGridType local_grid,
ArrayType& field )
{
// Update the boundary on each face of the cube.
// Create boundary indices for each plane.
Kokkos::Array<Cajita::IndexSpace<3>, 6> boundary_spaces;
// Store the boundary details in device-accessible fixed-size arrays.
Kokkos::Array<Kokkos::Array<int, 3>, 6> planes;
// Generate the boundary condition index spaces.
int count = 0;
for ( int d = 0; d < 3; d++ )
{
for ( int dir = -1; dir < 2; dir += 2 )
{
std::array<int, 3> plane = { 0, 0, 0 };
plane[d] = dir;
planes[count] = { 0, 0, 0 };
planes[count][d] = dir;

// Get the boundary indices for this plane (each one is a separate,
// contiguous index space).
auto boundary_space = local_grid->boundaryIndexSpace(
Cajita::Own(), Cajita::Cell(), plane );

Cajita::grid_parallel_for(
"boundary_update", exec_space, boundary_space,
KOKKOS_LAMBDA( const int i, const int j, const int k ) {
// Neumann boundary condition example
field( i, j, k, 0 ) =
field( i - plane[0], j - plane[1], k - plane[2], 0 );
} );
boundary_spaces[count] = local_grid->boundaryIndexSpace(
Cajita::Own(), Cajita::Cell(), planes[count][0],
planes[count][1], planes[count][2] );
count++;
}
}

// Update the boundary on each face of the cube. Pass the vector of index
// spaces to avoid launching 6 separate kernels.
Cajita::grid_parallel_for(
"boundary_update", exec_space, boundary_spaces,
KOKKOS_LAMBDA( const int b, const int i, const int j, const int k ) {
// Neumann boundary condition example
field( i, j, k, 0 ) = field( i - planes[b][0], j - planes[b][1],
k - planes[b][2], 0 );
} );
}

void finiteDifference()
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