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GPU
,→Grids and NDRange
Grids and NDRanges can be 1-dimensional, 2-dimensional, or 3-dimensional. 2-dimensional grids are common for screen-space operation such as pixel shaders. While 3-dimensional grids are useful for specifying many operations per pixel (such as a raytracer, which may launch 5000 rays per pixel).
The most important note is that Grids and NDRanges may not execute concurrently with each other. Some degree of sequential processing may happen. As such, communication across a Grid or NDRange is difficult to achieve(If thread #0 creates a Spinlock or Mutex waiting for thread #1000000 to communicate with it, modern hardware will probably never have the two threads executing concurrently with each other and the code would deadlock). In practice, the easiest mechanism for Grid or NDRange sized synchronization is to wait for the kernel to finish executing, and to have the CPU split tasks as appropriate. CPUs and GPUs can easily work as a team to accomplish their tasks.
= Architectures and Physical Hardware =
