update readme

README.md

@@ -1,20 +1,49 @@
 # ppScan
 
-## Overview
+## Related Work
 
-SCAN notations
+[SCAN Preliminaries](scan_preliminary.md)
 
-<img src="figures/scan-notations.png" height="200px" /> 
+## Design
 
-relations
+skeleton:
 
-def type | figure
---- | ---
-input/output | <img src="figures/scan-intro.png" height="200px"/>
-similarity predicate, eps-neighborhood | <img src="figures/def-1.png" height="200px" /> 
-core predicate | <img src="figures/def-2.png" height="200px" /> 
-cluster | <img src="figures/def-3.png" height="200px" /> 
-hub, outlier | <img src="figures/def-4.png" height="200px" /> 
+![ppSCAN skeleton](figures/ppscan-skeleton.png)
+
+data to operate with:
+
+data | type | functionality
+--- | --- | --- 
+`min_cn` | edge property array  | at beginning, min common neighbors to be similar, then `similar(-1)` or `not similar(-2)` indicator. some of them not evaluated by pruning
+`is_core` | vertex property array | at begining, bloom filter, after checking core second phase, the result of cores status for all vertices
+`is_non_core` | vertex property array | bloom filter, used in check core second phase
+`disjoint-set` | union-find set | inside two arrays, `parent` and `rank`, union-by-rank, compress-in-find-root, each tree represent a set
+`cluster_id` | vertex property array | for looking up min core vertex id in this cluster represented by root. in other words, `cluster_id[FindRoot(u)]` is this cluster id
+
+
+intentions in each phase:
+
+* Prune: initialize some values in `min_cn`, which can be easily computated with arithmetic operations instead of 
+set-intersection computations. There are two types, first is definitely not similar two vertices, second is defintely 
+similar two vertices.
+
+* CheckCoreFirstPhase: evaluate similarities for relationships from source vertex `u` to 
+destination vertex `v` for all `u<v` and update corresponding similarity from source vertex `v` to destination vertex `u`. 
+Min-max pruning is applied in this phase. Mark definite cores and definite non-cores with `is_core` and `is_non_core` array.
+
+* CheckCoreSecondPhase: since the existence of min-max pruning, some vertices can not be determined by two bloom filters, `is_core` and `is_non_core`, thus similarities sourcing from these vertices that are not evaluated 
+are evaluated and relationship is established for reversed edge.
+
+* ClusterCoreFirstPhase: without further evaluation of similarities, union similar core-cores.
+
+* ClusterCoreSecondPhase: some similarity predicates of core-cores are not know, evaluate them only when they are not in the same tree in the disjoint-set yet, 
+if they are similar, union them.
+
+* Trivial Preparing: Line 11 to 14 is for initializing `cluster_id` for looking up `cluster_id[FindRoot(u)]`.
+
+* ClusterNonCoreFirstPhase: evaluate some unknow similarities among cores and non-co res.
+
+* ClusterNonCoreSecondPhase: cluster non-cores when they are similar to cores 
 
 ## Project 
 

scan_preliminary.md

@@ -0,0 +1,15 @@
+## Overview
+
+SCAN notations
+
+<img src="figures/scan-notations.png" height="200px" /> 
+
+relations
+
+def type | figure
+--- | ---
+input/output | <img src="figures/scan-intro.png" height="200px"/>
+similarity predicate, eps-neighborhood | <img src="figures/def-1.png" height="200px" /> 
+core predicate | <img src="figures/def-2.png" height="200px" /> 
+cluster | <img src="figures/def-3.png" height="200px" /> 
+hub, outlier | <img src="figures/def-4.png" height="200px" />