Improve memory access of serial code

[Onotate]

The original code, though clear, uses many excessive code that can be changed to improve memory access and reduce looping operations:

• Use boolean for adjacency matrix instead of double since the edges are not weighted.
• Using memset and memcpy for initialization and copy of arrays instead of using loops.

The main calculation to update the page rank maybe refactored to reduce cache thrashing, but this may be a separate issue.

This issue thread will contain the runtime measurement of the original code, which will be posted later.

[Onotate]

Runtime measurement for original code: For generate_nice_graph:

0.00 seconds to generate the graph.
21 iterations achieved in 9.58 seconds
PageRank of vertex 0: 0.001000
PageRank of vertex 100: 0.001000
PageRank of vertex 200: 0.001000
PageRank of vertex 300: 0.001000
PageRank of vertex 400: 0.001000
PageRank of vertex 500: 0.001000
PageRank of vertex 600: 0.001000
PageRank of vertex 700: 0.001000
PageRank of vertex 800: 0.001000
PageRank of vertex 900: 0.001000
Sum of all pageranks = 1.000000000000, total diff = 0.000000000000, max diff = 0.000000000000 and min diff = 0.000000000000.
Total time taken: 9.5852 seconds.

For generate_sneaky_graph:

0.00 seconds to generate the graph.
43 iterations achieved in 9.93 seconds
PageRank of vertex 0: 0.002541
PageRank of vertex 100: 0.001726
PageRank of vertex 200: 0.001494
PageRank of vertex 300: 0.001302
PageRank of vertex 400: 0.001127
PageRank of vertex 500: 0.000962
PageRank of vertex 600: 0.000800
PageRank of vertex 700: 0.000641
PageRank of vertex 800: 0.000483
PageRank of vertex 900: 0.000322
Sum of all pageranks = 1.000000000000, total diff = 1.168591825342, max diff = 0.624703182089 and min diff = 0.000000000000.
Total time taken: 9.9311 seconds.