PMacc data types [Buffer]

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This page give an overview of the most impotent data types in PMacc.

Naming

Buffer = is a container that point or holds memory

array based buffers

• Buffers are located in libPMacc/include/memory/buffers
• Buffers can be container of real memory those are located on an accelerator/host or container those were a combination real memory buffers.

buffers with real memory

In the most cases this buffer types are a combination of [memory location]Buffer (the interface), Buffer (generic interface) and [memory location]BufferIntern (implementation).

• DeviceBuffer/ DeviceBufferIntern
  • contains device memory
  • memory is set to zero on initialization
  • line by line aligned (if multi dimensional)
  • number of elements (current size) is available on device (optional)
  • can point to existing device memory (optional)
• HostBuffer/ HostBufferIntern
  • contains host memory
  • memory is set to zero on initialization
  • also multi dimensional memory is not aligned
• Exchange/ExchangeIntern
  • buffer for communicate guarding cells (ghost cells)
  • contains host buffer
  • point to a subset of existing device buffer (host and device size are the same)
  • linear device double buffer of subset were the device buffer points to (only existing on multi dimensional exchanges) [ used to speed up memory copies from host2device and device2host ]
• MappedBuffer
  • contains host buffer those can directly accessed from device
  • memory is set to zero on initialization
  • same interface like DeviceBuffer
  • not aligned

combined Buffer

• GridBuffer
  • complex buffer those contains DeviceBuffer, HostBuffer
  • ExchangeBuffer can be added at runtime for every side of the memory (1D -- <=2 exchanges, 2D -- <= 8 exchanges, 3D -- <=26 exchanges)
  • contains methods for asynchronous communication of the exchanges
• MultiGridBuffer
  • create multiple GridBuffer of the same native data type and size in one big memory chunk
  • every GridBuffer can accessed by a enum
  • exchanges can be set separate for on GridBuffer or for all
  • the used iterator MultiBox has a small memory footprint in contrast to multiple GridBuffers