Automated Design Space Exploration (DSE) is a crucial methodology for efficiently optimizing Field-Programmable Gate Array (FPGA) designs targeted towards Artificial Intelligence (AI) and High-Performance Computing (HPC) applications. Given the inherent complexity and vast configuration possibilities within FPGAs, manual exploration of all possible design choices becomes quickly infeasible. Instead, automated DSE techniques systematically navigate the design space, searching for optimal design configurations that best balance conflicting objectives such as performance, power consumption, and resource utilization, all while respecting imposed design constraints. The process encompasses defining the design space, setting objectives and constraints, selecting appropriate exploration algorithms, employing suitable tools, and critically analyzing the results to pinpoint the best design choices.
The design space encompasses a multi-dimensional parameter space containing all the adjustable variables influencing an FPGA design's characteristics. These variables span across different abstraction levels, ranging from high-level architectural choices to low-level implementation settings. Common categories of design space parameters include:
Hardware Architecture: This defines the fundamental organization of the hardware accelerators, including the number of processing elements (PEs), the type of interconnections between PEs (e.g., mesh, crossbar), and the overall dataflow topology (e.g., systolic array, dataflow graph). For example, in a CNN accelerator, the number of parallel multipliers and adders within each PE, and the number of PEs in the array.
Memory Organization: This involves configuring the on-chip memory hierarchy, including the size, organization (e.g., single-port, dual-port), and placement of on-chip memories (e.g., block RAMs, distributed RAMs). It also includes strategies for managing external memory access, such as using DMA controllers and burst transfers. For example, determining the size of the L1 and L2 caches in a memory subsystem or the depth of FIFOs used for buffering data between processing stages.
Dataflow Transformations: These are techniques used to reorganize the dataflow of the application, often to improve data locality, increase parallelism, or reduce memory access requirements. Examples include loop unrolling, loop tiling, loop fusion, and data reordering. For instance, applying loop tiling to a matrix multiplication kernel to improve data reuse within on-chip memory.
Synthesis Settings: These are parameters that control the behavior of the synthesis tool, which translates the high-level hardware description into a gate-level netlist. Examples include optimization goals (e.g., speed, area), clock frequency constraints, and resource allocation directives. For instance, instructing the synthesis tool to prioritize minimizing latency versus minimizing the number of LUTs used.
Place-and-Route Constraints: These are constraints used to guide the physical implementation of the design on the FPGA, including placement constraints that specify the location of specific components and ....
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