PIConGPU domain definitions

You are here: Home > Developer Documentation > PIConGPU domain definitions

---

Current naming scheme

This page describes the internal naming scheme for domain and window offsets and sizes in PIConGPU as described in this issue.

objects

• domain = contiguous volume on one or all GPUs
• window = any part of a domain

object attributes

attribute	type	notes
.size	uint	size of an object
.offset	int	offset of an object to its next higher hierarchy

• offsets are exclusive and always relative to the element that is above it in the hierarchy

hierarchy

• local = the object is located on the current ("my") GPU, no guards
• global = the currently simulated volume over all GPUs, no guards
• total = takes parts into account that are not in the global volume, e.g. previous areas that have been gone due to the sliding window

this results in

• global:
  • globalDomain.size = size of currently simulation volume on all GPUs
  • globalDomain.offset = offset caused due to slides: offset to the totalDomain
  • globalWindow.size = size of the current/selected moving window (cutting away areas of the globalDomain that are before/after the window)
  • globalWindow.offset = offset of moving window from the first GPU: offset to the globalDomain
• local:
  • localDomain.size = size of my GPU
  • localDomain.offset = beginning of my local domain in the global Domain
  • localWindow.size = size of the volume of the moving window on my GPU
  • localWindow.offset = offset of my moving window part from the start of the global window

Special use cases

• My GPU is not contained in the moving window.
  • localWindow.size == 0
  • localWindow.offset == undefined
• An interface, lets say the gasProfiles, may needs an inclusive domain offset like
  • localDomain.offset+globalDomain.offset (1)
  • how to name the result (1) in the interface?
  • suggestion: localDomainToTotal = (1)
  • note: usually, as defined above, localDomain means localDomainToGlobal because global is the next higher hierarchy.

Old naming scheme (deprecated)

• domainSize: size of the simulation grid for a GPU

• domainOffset: offset of the simulation grid of a GPU within the total simulation grid

• globalDomainSize: size of the currently computed part of the simulation grid (moving window)

• globalDomainOffset: offset of the currently computed part of the simulation grid (moving window) within the total simulation grid

• localDomainOffset: offset of the simulation grid of a GPU from the start of the currently computed part (moving window). 0 for all GPUs for which domainOffset > globalDomainOffset

In the below image, the currently computed part of the simulation grid (moving window) is marked as a hatched area. Note that for simulations which do not use moving window, the currently computed part of the simulation grid always spans the total simulation grid.