# Improving Transaction Speed and Scalability of Blockchain Systems via Parallel Proof of Work +
## 4 Results of Experimental Evaluation
### Evaluation in Local Environment
#### 4.2.2 Results  
For parallel mining, the test was done with different difficulty levels for different peers. The test was conducted for a large number of blocks continuously. Figures 8 and 9 represent the time required to solve any 15 consecutive blocks by a different number of peers in 6D and 10D difficulty levels, respectively. For 6D difficulty, the bock solving time differences were not that significant compared to different number of peers. For example, the highest time required to solve one block was around 13.5 min when the test has been done for one peer. Again, the highest time required to solve one block was around 14.25 min for 19 peers. If the lowest block-solving time is considered, the time required to solve one block was almost same for one peer, seven peers and 19 peers. However, when the average time is considered for different numbers of peers, a small but significant result has been found. It seems that when the number of peer increase the average block solving time decrease. The average block solving time for one peer, seven peers, 13 peers, 19 peers, 25 peers and 31 peers were 7.92, 8.41, 8.79, 9.39 and 9.72 min respectively. With increase of 6 peers, the block solving time decreased to 0.45 min on average. Figure 8: Time to solve 15 consecutive blocks by varying number of peers in 6D difficulty. The next test increased the difficulty level to 7D, 8D, 9D and 10D, and this increased the block creation time. For example, the average block solving time difference for 7D was 0.55 min. It was 1.33 min for 8D level of difficulty. The average time differences were 2.65 min and 5.51 min for 9D and 10D respectively with the increase of number of peers. Figure 9 represents the time required to solve any 15 consecutive block by different number of peers in 10D difficulty level. It shows more significant result compared to the 6D difficulty. The block-solving time difference between one peer and 31 peers parallel working environment was significantly more compared to the result in 6D difficulty level. For example, the highest and lowest time required to solve a block in case of one peer were around 75 min and 50 min respectively. For 31 peers, those were 40 min and 31 min respectively. If the average times are considered, those are 58.84, 53.63, 48.48, 40.03 and 36.78 min for one peer, seven peers, 13 peers, 19 peers and 31 peers, respectively, with an average of 5.51 min' time difference to create one block. Figure 10 represents the average time required to solve a block in a different difficulty level with a different number of peers. The required time increased with the increase of number of peers in the same difficulty and increased with the increase of difficulty for the same number of peers. Also, the difference of average time required increased with the increase of the difficulty level. For example, in 6D, the time difference was almost 2.2 min compared with one and 31 peers. In the case of 10D difficulty, it was 22.07 min. This shows that the proposed algorithm was more efficient with the increase of both peers and difficulty level. To compare parallel mining with traditional solo mining, a similar environment was created. The experiment was done for different difficulty levels with different numbers of peers. The block creation time does not depend on the number of peers, but on the level of difficulty. Figure 11 shows the solo mining for different difficulty levels for any 15 consecutive blocks. The highest and lowest time required to solve one block in 10D difficulty was around 75 and 49 min. For the 6D difficulty it is around 12 min and nine minutes respectively. The average time increased with the increase of difficulty level. Figure 9: Time to solve 15 consecutive blocks by varying number of peers in 10D difficulty. When we compared the solo mining average block creation time in respect to parallel mining for 31 peers, we found similar results for the difference between one peer and 31 peers in parallel mining (Figure 12).