tailieunhanh - Electromagnetic Waves Propagation in Complex Matter Part 16

Tham khảo tài liệu 'electromagnetic waves propagation in complex matter part 16', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Optimization of Parallel FDTD Computations Based on Program Macro Data Flow Graph Transformations 287 Fig. 10. Comparison of Speedup for the Redeployment Method with the CDC Algorithm. Optimizing algorithm execution time ms 50cpu 25cpu 10cpu Processors Redeployment computational area 1 Redeployment computational area2 CDC computational area 1 CDC computational area 2 Fig. 11. Comparison of the Total Optimization Execution Time for Redeployment and CDC Algorithm. 288 Electromagnetic Waves Propagation in Complex Matter Unfortunately we have observed some unfavorable features of this algorithm. The first one is that the execution time of this algorithm Figure 11 was from 25 to 50 times longer in comparison to redeployment algorithm. It can completely eliminate the use of CDC algorithm for computational areas with large number of cells. In our experiments we could not simulate areas larger than 1000 cells. It is because large number of messages are generated. We observed also that CDC algorithm is very sensitive to two simulation parameters MinWeight and initial value of TTL time. These parameters are decisive for messages lifespan and unfortunately their values considerably depend on the shape of computational area. 6. Hierarchical algorithm Based on the results presented in the previous section we can observe that the redeployment algorithm is much faster than the CDC algorithm. The convergence time of the redeployment algorithm is almost two times shorter in comparison to CDC. However for system configurations with a big number of processors the parallel speedup of the FDTD programs obtained using the redeployment method is lower than that obtained with the use of the CDC algorithm. A difficult problem in CDC is setting the initial values of the parameters MinWeight and TTL time. It is especially true for a large number of executive processors. Taking into considerations all pros and cons of the two methods we propose a hierarchical method of FDTD program .