void init()
{
/* copy singleton simulationBox data to simbox simBox holds global and*
* local SimulationSize and where the local SimArea is in the greater *
* scheme using Offsets from global LEFT, TOP, FRONT */
PMACC_AUTO(simBox, Environment<DIM2>::get().SubGrid().getSimulationBox());
/* Recall that in types.hpp the following is defined: *
* typedef MappingDescription<DIM2, math::CT::Int<16,16> > MappingDesc; *
* where math::CT::Int<16,16> is arbitrarily(!) chosen SuperCellSize and DIM2 *
* is the dimension of the grid. *
* Expression of 2nd argument translates to DataSpace<DIM3>(16,16,0). *
* This is the guard size (here set to be one Supercell wide in all *
* directions). Meaning we have 16*16*(2*grid.x+2*grid.y+4) more *
* cells in GridLayout than in SimulationBox. */
GridLayout<DIM2> layout( simBox.getLocalSize(),
MappingDesc::SuperCellSize::toRT());
/* getDataSpace will return DataSpace( grid.x +16+16, grid.y +16+16) *
* init stores the arguments internally in a MappingDesc private *
* variable which stores the layout regarding Core, Border and guard *
* in units of SuperCells to be used by the kernel to identify itself.*/
evo.init(MappingDesc(layout.getDataSpace(), 1, 1));
buff1 = new Buffer(layout, false);
buff2 = new Buffer(layout, false);
Space gardingCells(1, 1);
for (uint32_t i = 1; i < traits::NumberOfExchanges<DIM2>::value; ++i)
{
/* to check which number corresponds to which direction, you can *
* use the following member of class Mask like done in the two *
* lines below: *
* DataSpace<DIM2>relVec = Mask::getRelativeDirections<DIM2>(i); *
* std::cout << "Direction:" << i << " => Vec: (" << relVec[0] *
* << "," << relVec[1] << ")\n"; *
* The result is: 1:right(1,0), 2:left(-1,0), 3:up(0,1), *
* 4:up right(1,1), 5:(-1,1), 6:(0,-1), 7:(1,-1), 8:(-1,-1) */
/* types.hpp: enum CommunicationTags{ BUFF1 = 0u, BUFF2 = 1u }; */
buff1->addExchange(GUARD, Mask(i), gardingCells, BUFF1);
buff2->addExchange(GUARD, Mask(i), gardingCells, BUFF2);
}
/* Both next lines are defined in GatherSlice.hpp: *
* -gather saves the MessageHeader object *
* -Then do an Allgather for the gloabalRanks from GC, sort out *
* -inactive processes (second/boolean ,argument in gather.init) and*
* save new MPI_COMMUNICATOR created from these into private var. *
* -return if rank == 0 */
MessageHeader header(gridSize, layout, simBox.getGlobalOffset());
isMaster = gather.init(header, true);
/* Calls kernel to initialize random generator. Game of Life is then *
* initialized using uniform random numbers. With 10% (second arg) *
* white points. World will be written to buffer in first argument */
evo.initEvolution(buff1->getDeviceBuffer().getDataBox(), 0.1);
}
void init()
{
/* subGrid holds global and
* local SimulationSize and where the local SimArea is in the greater
* scheme using Offsets from global LEFT, TOP, FRONT
*/
const SubGrid<DIM2>& subGrid = Environment<DIM2>::get().SubGrid();
/* The following sets up the local layout which consists of the actual
* grid cells and some surrounding cells, called guards.
*
* ASCII Visualization: example taken for 1D,
* distributed over 2 GPUs, only 1 border shown between those two GPUs
* assuming non-periodic boundary conditions.
* In a N-GPU or periodic example, border cells guard cells exist in each direction.
* _______GPU 0________ _______GPU 1________
* | 0 | 1 | 2 | 3 | 4 | | 3 | 4 | 5 | 6 | 7 | <-- Global (super)cell idx
* |___|___|___|___|___| |___|___|___|___|___|
* |___Core____|Bor|Gua| |Gua|Bor|___Core____|
* |___________|der|rd_| |rd_|der|___________|
* |__"real" cells_|***| |***|__"real" cells_|
*
* |***| Clones cells which correspond to the border cells of the neighbor GPU
* (sometimes also called "ghost" or "halo" cells/region)
*
* Recall that the following is defined:
* typedef MappingDescription<DIM2, math::CT::Int<16,16> > MappingDesc;
* where math::CT::Int<16,16> is arbitrarily(!) chosen SuperCellSize
* and DIM2 is the dimension of the grid.
* Expression of 2nd argument translates to DataSpace<DIM3>(16,16,0).
* This is the guard size (here set to be one Supercell wide in all
* directions). Meaning we have 16*16*(2*grid.x+2*grid.y+4) more
* cells in GridLayout than in the SubGrid.
* The formula above is SuperCellSize * TotalNumGuardCells with (in this case)
* SuperCellSize = 16*16 (16 cells in 2 dimensions)
* TotalNumGuardCells = 2 * grid.x (top and bottom)
* + 2 * grid.y (left and right)
* + 4 (the corners)
*/
GridLayout<DIM2> layout( subGrid.getLocalDomain().size,
MappingDesc::SuperCellSize::toRT());
/* getDataSpace will return DataSpace( grid.x +16+16, grid.y +16+16) *
* MappingDesc stores the layout regarding Core, Border and Guard *
* in units of SuperCells. *
* This is saved by init to be used by the kernel to identify itself. */
evo.init(layout.getDataSpace(), Space::create(1));
buff1 = new Buffer(layout, false);
buff2 = new Buffer(layout, false);
/* Set up the future data exchange. In this case we need to copy the
* border cells of our neighbors to our guard cells, since we only read
* from the guard cells but never write to it.
* guardingCells holds the number of guard(super)cells in each dimension
*/
Space guardingCells(1, 1);
for (uint32_t i = 1; i < traits::NumberOfExchanges<DIM2>::value; ++i)
{
/* to check which number corresponds to which direction, you can *
* use the following member of class Mask like done in the two *
* lines below: *
* DataSpace<DIM2>relVec = Mask::getRelativeDirections<DIM2>(i); *
* std::cout << "Direction:" << i << " => Vec: (" << relVec[0] *
* << "," << relVec[1] << ")\n"; *
* The result is: 1:right(1,0), 2:left(-1,0), 3:up(0,1), *
* 4:up right(1,1), 5:(-1,1), 6:(0,-1), 7:(1,-1), 8:(-1,-1) */
/* types.hpp: enum CommunicationTags{ BUFF1 = 0u, BUFF2 = 1u }; */
buff1->addExchange(GUARD, Mask(i), guardingCells, BUFF1);
buff2->addExchange(GUARD, Mask(i), guardingCells, BUFF2);
}
/* Both next lines are defined in GatherSlice.hpp: *
* -gather saves the MessageHeader object *
* -Then do an Allgather for the gloabalRanks from GC, sort out *
* -inactive processes (second/boolean ,argument in gather.init) and*
* save new MPI_COMMUNICATOR created from these into private var. *
* -return if rank == 0 */
MessageHeader header(gridSize, layout, subGrid.getLocalDomain().offset);
isMaster = gather.init(header, true);
/* Calls kernel to initialize random generator. Game of Life is then *
* initialized using uniform random numbers. With 10% (second arg) *
* white points. World will be written to buffer in first argument */
evo.initEvolution(buff1->getDeviceBuffer().getDataBox(), 0.1);
}
