diff toolboxes/FullBNT-1.0.7/graph/reachability_graph.m @ 0:e9a9cd732c1e tip

first hg version after svn

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/toolboxes/FullBNT-1.0.7/graph/reachability_graph.m	Tue Feb 10 15:05:51 2015 +0000
@@ -0,0 +1,19 @@
+function C = reachability_graph(G)
+% REACHABILITY_GRAPH C(i,j) = 1 iff there is a path from i to j in DAG G
+% C = reachability_graph(G)
+
+if 1
+  % expm(G) = I + G + G^2 / 2! + G^3 / 3! + ...
+  M = expm(double(full(G))) - eye(length(G));
+  C = (M>0);
+else
+  % This computes C = G + G^2 + ... + G^{n-1}
+  n = length(G);
+  A = G;
+  C = zeros(n);
+  for i=1:n-1
+    C = C + A;
+    A = A * G;
+  end
+  C = (C > 0);
+end