Early prototyping of the various workloads identifies some common trends and clear conclusions:
The iFFT throughput (which was prototyped for the 4K-pt size as compared to the reduced-footprint 2K-pt size) of 100 Msps comfortably exceeds the 8 Msps requirement above assuming a 1G BP OPs/sec throughput. This conclusion carries over safely to the 2K-pt size identified in the system modeling phase.
Most of the remaining compute workloads that operate pixel-by-pixel achieve a throughput in the mid 400 Msps range, with a few kernels achieving two to three times this much. It follows then, one straightforward approach is to design a SAR BP engine capable of ~400 Msps throughput based on these early prototype kernel architectures. Note the
fmod_floor()prototype kernel does not meet this 400 Msps throughput target. Its implementation needs to be optimized using code refactoring and improved software pipelining (or it can split across multiple instances). The design phase covers these details.The memory footprint of these kernels is large across the board. Each kernel typically requires a single compute tile but burns 2 to 4 tiles in memory.
Based on this early estimate of 31 tiles and the expectation that the size of the
ifft2k()kernel frees up 5 or 6 tiles, it makes sense given the array geometry to provision for a \(4\times 8\) engine configuration with 32 tiles. This provides some resource margin.