# Harvesting the Aggregate Computing Power of Commodity Computers for Supercomputing Applications
## 4 Experimental Evaluation and Results
### DeepStack Cluster
Theoretical improvement in performance should scale linearly for fully parallelizable tasks, but in a real implementation, a 10% loss in speedup on two-node and a 15% loss in speedup occurred for the three-node cluster. This loss was entirely due to the latency of the network (Ethernet) cable and switch performance. Adding more nodes in a cluster increases the speedup in latency and TAT, decreases the average waiting time of individual processes, and increases communication cost. In linear speedup, per [PERSON]'s law on a fixed parallelizability level in a program, if we increase the number of processors, Torque exhibits an approximately linear increase in speedup as we add new processors. For the sublinear speed up, if the program has an %(<100%) sequential part, it exhibits sublinear speedup on Torque. The exact penalty can be computed by [PERSON]'s equation and implementation of the program. During experimentation, single compute node, FCFS scheduling performance is used as a benchmark which has execution order as given in Table 5 below and the average baseline performance is seen in Table 6. Note: AT: Arrival time, BT: Burst time, CT: completion time, TAT: Turn around time, and WT: waiting time. \begin{table}
\begin{tabular}{c c c c} \hline
**SNo.** & **Job Id** & **Arrival Time** & **CPU Burst Time** \\ \hline
1 & P1 & 4 & 200 \\
2 & P2 & 10 & 500 \\
3 & P3 & 6 & 400 \\
4 & P4 & 2 & 300 \\
5 & P5 & 5 & 200 \\
6 & P6 & 3 & 100 \\
7 & P7 & 12 & 250 \\
8 & P8 & 14 & 320 \\
9 & P9 & 20 & 250 \\
10 & P10 & 22 & 150 \\ \hline \end{tabular}
\end{table} 
Table 4: Sample Workload. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline P4 & P6 & P1 & P5 & P3 & P2 & P7 & P8 & P9 & P10 \\ \hline \end{tabular}
\end{table} 
Table 5: Torque job execution order on a single node. The cluster-level performance of DeepStack with a 2-node cluster and DeepStack with a 3-node cluster and the expected speedup with the actual gain from the setup is also seen in Table 7 and Table 8, respectively. As per [PERSON]'s law in this case the speedup in CT and TAT should be twice as of the single processor benchmark but due to internal latencies, it is decreased by 10% for the 2-node cluster and by 15% for the 3-node cluster as seen on Table 9. This is because the performance of clusters declines as described by [PERSON]'s law. This happens because, there is a delay from locking of processes by a scheduling algorithm used, high internal bandwidth consumption, and poor performance of Ethernet cable capacity. The use of Gigabits per second Ethernet platform among Pbs_servers and compute nodes helps to get better performance. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Process** & **AT** & **BT** & **Start** & **CT** & **TAT** & **WT** \\ \hline P4 & 2 & 300 & 2 & 302 & 300 & 0 \\ P6 & 3 & 100 & 302 & 402 & 399 & 299 \\ P1 & 4 & 200 & 402 & 602 & 598 & 398 \\ P5 & 5 & 200 & 602 & 802 & 797 & 597 \\ P3 & 6 & 400 & 802 & 1202 & 1196 & 796 \\ P2 & 10 & 500 & 1202 & 1702 & 1692 & 1192 \\ P7 & 12 & 250 & 1702 & 1952 & 1940 & 1690 \\ P8 & 14 & 320 & 1952 & 2272 & 2258 & 1938 \\ P9 & 20 & 250 & 2272 & 2522 & 2502 & 2252 \\ P10 & 22 & 150 & 2522 & 2672 & 2650 & 2500 \\  & & **Avg. Baseline** & **1443** & **1433.2** & **1166.2** \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Torque job execution order on a single node. \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **DeepStack** & **Speedup** & **Expected Speedup** \\ \hline Avg. CT & 804.315 & 1443/804.315 = 1.79 & 2 \\ Avg. TAT & 791.818 & 1.8 & 2 \\ Avg. WT & 525.81 & 2.12 & NA \\ Avg. Latency & 8.28 & NA & NA \\ \hline \hline \end{tabular}
\end{table} 
Table 7: Torque job execution order on 2-node cluster. \begin{table}
\begin{tabular}{c c c} \hline \hline  & **DeepStack** & **Speedup** \\ \hline Avg. CT & 583.75 & 1443/583.75 = 2.47 \\ Avg. TAT & 573.8 & 2.49 \\ Avg. WT & 301.5 & 3.87 \\ Avg. Latency & 8.25 & NA \\ \hline \hline \end{tabular}
\end{table} 
Table 8: Torque job execution order on 3-node cluster.