Reduce fragment size

[yecol]

as titled, reduce the fragment size with potential optimization (e.g., varint)

• [ ] baseline test, compare with Plato, GraphX and other systems....
• [x] optimization-1: varint, considering compatibility, co-exists with current fragments.
• [x] optimization-2: perfect hashing, (advise @luoxiaojian)
• [x] test and report effectiveness.

[sighingnow]

baseline test, compare with Plato, GraphX and other systems....

Systems:

• GraphScope
• Plato
• GraphX
• Giraph
• Gemini

Datasets:

• soc-LiveJournal1
• soc-twitter-2010
• soc-sinaweibo
• soc-orkut

Algorithms:

• pagerank
• sssp

Measurements:

• Peek memory
  • during running graph
  • during running application
• Memory after loading graph
• Running time
  • loading graph
  • running application

@yecol @vegetableysm Any comments on the plan above?

[sighingnow]

Refer to https://github.com/alibaba/libgrape-lite/blob/master/Performance.md

[yecol]

Sounds like a good plan!