Finite-difference time-domain on the cell/B.E. processor

Abstract

Finite-Difference Time-Domain (FDTD) is a kernel usedto solve problems in electromagnetics applications such as microwave tomography. It is a data-intensive and computation-intensive problem. However, its computation scheme indicates that an architecture with SIMD support has the potential to bring performance improvement over traditional architectures without SIMD support. The Cell Broadband Engine (Cell/B.E.) processor is an implementation of a heterogeneous multicore architecture. It consists of one conventional microprocessor, PowerPC Processor Element (PPE), and eight SIMD co-processor elements, Synergistic Processor Elements (SPEs). One unique feature of an SPE is that it has 128-entry 128-bit uniform registers which support SIMD. Therefore, FDTD may be mapped well on Cell/B.E. processor. However, each SPE can directly access only 256KB local store (LS) both for instructions and data. The size of LS is much less than what is needed for an accurate simulation of FDTD which requires large number of fine-grained Yee cells. In this paper, we design the algorithm on Cell/B.E. by efficiently using the asynchronous DMA (direct memory access) mechanism available on an SPE transferring data between its LS and the main memory via the high bandwidth bus on-chip EIB (Element Interconnect Bus). The new algorithm was run on an IBM Blade QS20 blades running at 3.2GHz. For a computation domain of 600 × 600 Yee cells, we achieve an overall speedup of 14.14 over AMD Athlon and 7.05 over AMD Opteron at the processor level.

Microwave tomography for breast cancer detection on Cell broadband engine processors

“…Similar communication-computation overlapping is done for E zy and H x . This approach is significantly different from our previous work (naive mapping) in[38,36], where we do not overlap the computation with the DMA transfers. That is, SPE calculates fields, such as E zx , then issues DMA commands to store E zx back to the main memory.…”

“…Fig. 5 shows the comparison between our earlier work [36] (naïve approach) and the current optimized work with overlapping computations and communications. As can be seen, the optimized FDTD algorithm performs significantly better than the naïve algorithm.…”

“…In Fig. 6, we compared the overall performance of optimized microwave tomography to our original work [36]. We do this by separating the execution times of the PPE (executing GA, initialization, near to far field transformation) and SPEs (executing FDTD).…”

“…3 Synchronization is necessary between SPEs in the FDTD algorithm. In [36], we investigated two synchronization mechanisms, mailbox and SPE signal notification registers. Since we do not find too much of performance difference between these two mechanisms, in this work, we use mailbox synchronization mechanism.…”

“…In [36,37], we parallelized FDTD on Cell BE and compared the results with a shared memory architecture and a cluster of distributed memory multicores. Cell BE achieved a speedup of 14.14 over AMD Athlon and 7.05 over AMD Opteron at the processor chip level.…”