Small optimization to dpp_single (#5)

* Small optimization

Calculating cliques and plex overlap is one of the slowest steps in `dpp_single`. This optimization calculates overlap only for those cliques and plexes that are not already merged into a single community.

* Bugfix removing unnecessary duplicate calls

The `dpp_single` function was called twice per iteration, rather than once due to a typo.

Author: nathanntg

src/dpp/dpp_iter.m

@@ -5,7 +5,7 @@
 %   community.
 
 % reuse previous calculations
-if ~exist('cliq1', 'var')
+if ~exist('cliq_and_plex1', 'var')
     [cliq_and_plex1, communities1] = dpp_single(a1, k, m);
 end
 

src/dpp/dpp_single.m

@@ -77,6 +77,12 @@
     % remaining cliques/plexes
     js = (i+1):num_cliq_and_plex;
 
+    % optimization: only consider those that are not already part of the same community
+    js = js(communities(js) ~= communities(i));
+    if isempty(js)
+        continue;
+    end
+    
     % vector of overlaps between remaining cliques/plexes and clique/plex i
     overlap = sum(cliq_and_plex(js, cliq_and_plex(i, :)), 2);