Queue - March/April 2008

finer pieces that can be solved cooperatively in parallel. The programming model scales transparently to large numbers of processor cores: a compiled CUDA program executes on any number of processors, and only the runtime system needs to know the physical processor count.

THE CUDA PARADIGM

CUDA is a minimal extension of the C and C++ programming languages. The programmer writes a serial program that calls parallel kernels, which may be simple functions

SIMT (single-instruction, multiple-thread). ³ The SM maps each thread to one SP scalar core, and each scalar thread executes independently with its own instruction address and register state. The SM SIMT unit creates, manages, sched-

or full programs. A kernel executes in parallel across a set of parallel threads. The programmer organizes these threads into a hierarchy of grids of thread blocks. A thread block is a set of concurrent threads that can cooperate among themselves through barrier synchronization and shared access to a memory space private to the block. A grid is a set of thread blocks that may each be executed independently and thus may execute in parallel.

When invoking a kernel, the programmer specifies the number of threads per block and the number of blocks

ules, and executes threads in groups of 32 parallel threads called warps. (This term originates from weaving, the first parallel thread technology.) Individual threads composing a