# PLORC: A Pipelined Lossless Reference-Free Compression Architecture for FASTQ Files
## 4 Results and Discussion
### Experiment Information  
We executed different compression algorithms on the FASTQ files listed in Table 7. As discussed in Section 1, CPU-based genomic-specific compression algorithms [19; 20; 21] have limited throughput rates. Therefore, these algorithms are not within the comparing scope of this article.  
Our PLORC compressor and decompressor are implemented on a Zynq UltraScale+ ZCU102 Evaluation Board by Vivado 2022.2.  
We conducted compression experiments on Gzip [47], LZ4 [30], and Zstd [31] to measure their CRs (compression ratios). The definition of CR is shown in Equation (1). The CRs of the tested compression algorithms are shown in Table 8. A comparison of the CRs is shown in Figure 21. The x-axis of Figure 21 represents the 'Dataset Number' in Table 7. The y-axis means the ratio between the CR of the tested algorithm and the minimum CR on the same dataset. In addition, we implemented Gzip [48], LZ4, and Zstd [49] on a Zynq UltraScale+ ZCU102 Evaluation Board to measure their TPRs (throughput rates) and resource consumption.  
The throughput rates and power consumption results of the FPGA-based algorithms are shown in Table 9. The resource consumption is shown in Table 10. 'Com' means 'compressor' and 'Decom' means 'decompressor' in Tables 9 and 10. The throughput rate and resource consumption results of REBA are calculated from the results in [16; 50].  
To provide a comprehensive evaluation, we introduce Power Efficiency (PE), as shown in Table 9. The definition of PE is shown in Equation (2).  
\[\text{CR}=\frac{\text{original file size}}{\text{compressed file size}}, \tag{1}\]  
\begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline \multicolumn{2}{c}{**Gzip on FPGA 1**} & \multicolumn{2}{c}{**LZ4 on FPGA**} & \multicolumn{2}{c}{**Zstd on FPGA**} & \multicolumn{2}{c}{**REBA 2**} & \multicolumn{2}{c}{**PLORC**} \\ \hline \multicolumn{2}{c}{**Com 3**} & **Com** & **Decom** & **Com** & **Decom** & **Com** & **Com** & **Decom** \\ \hline FPGA type & ZCU102 & ZCU102 & ZCU102 & ZCU102 & ZCU102 & Stratix V & ZCU102 & ZCU102 \\ LUTs 4  & 8.2K & 3K & 0.6K & 22K & 17.7K & 2.7K & 5.6K \\ Flip-Flops & 8.1K & 3K & 0.5K & 22K & 13.8K & 129K & 5.3K & 8.7K \\ BRAM & 24.5 & 14 & 32 & 32 & 64 & 0.8K & 0 & 0 \\ \hline \hline \end{tabular}  
* There was no open-source code about the Gzip decompressor in [48]. 2 There were no experiment results about its decompressor in [16]. 3 \({}^{\text{Com}}\)’ means ‘compressor’ and ’Decom’ means ‘decompressor’. 4 \({}^{\text{LUT}}\) (Look-Up Table), FF (Flip-Flop), and BRAM (Block RAM) are basic types of hardware resources on FPGA. The LUTs in ZCU102 are 6-input LUTs [51], and those in Stratix V are detailed in [52].  
\end{table}
Table 9: The throughput rates and power consumption of the FPGA-based compressors.  
\begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multicolumn{2}{c}{**Dataset**} & & & & \\
**Number** & **Gzip** & **LZ4** & **Zstd** & **PLORC** \\ \hline
1 [42] & 3.00 & 1.91 & 2.99 & 3.19 \\
2 [42] & 3.10 & 1.96 & 3.01 & 3.26 \\
3 [43] & 3.13 & 2.26 & 3.06 & 3.18 \\
4 [43] & 2.93 & 1.98 & 2.98 & 3.01 \\
5 [44] & 3.05 & 1.89 & 2.97 & 3.37 \\
6 [44] & 2.83 & 1.77 & 2.82 & 3.08 \\
7 [45] & 2.77 & 1.69 & 2.72 & 3.16 \\
8 [45] & 2.75 & 1.68 & 2.70 & 3.03 \\
9 [46] & 2.84 & 1.75 & 2.80 & 3.06 \\
10 [46] & 2.76 & 1.74 & 2.76 & 3.01 \\ \hline \hline \end{tabular}
\end{table}
Table 8: The compression ratios of tested compression algorithms.