diff --git a/config.h b/config.h
index 8e5c6a4..e766a43 100644
--- a/config.h
+++ b/config.h
@@ -1,6 +1,9 @@
 /* config.h.  Generated from config.h.in by configure.  */
 /* config.h.in.  Generated from configure.ac by autoheader.  */
 
+/* "whether graphviz is enable" */
+#define ENABLE_GRAPHVIZ test "x$enable_graphviz" = "xyes"
+
 /* Define to 1 if you have the <dlfcn.h> header file. */
 #define HAVE_DLFCN_H 1
 
diff --git a/config.h.in b/config.h.in
index 4aa7a2f..c74bb06 100644
--- a/config.h.in
+++ b/config.h.in
@@ -1,5 +1,8 @@
 /* config.h.in.  Generated from configure.ac by autoheader.  */
 
+/* "whether graphviz is enable" */
+#undef ENABLE_GRAPHVIZ
+
 /* Define to 1 if you have the <dlfcn.h> header file. */
 #undef HAVE_DLFCN_H
 
diff --git a/configure.ac b/configure.ac
index 66a2beb..b6fd07b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -45,6 +45,7 @@ AC_ARG_ENABLE(debug,
 
 AM_CONDITIONAL(ENABLE_DEBUG, test "x$enable_debug" = "xyes")
 AM_CONDITIONAL(ENABLE_GRAPHVIZ, test "x$enable_graphviz" = "xyes")
+AC_DEFINE(ENABLE_GRAPHVIZ, test "x$enable_graphviz" = "xyes", "whether graphviz is enable")
 
 
 PKG_CHECK_MODULES(DEPS, [libpcre check])
diff --git a/include/r3_gvc.h b/include/r3_gvc.h
index 012470d..e6ef6ea 100644
--- a/include/r3_gvc.h
+++ b/include/r3_gvc.h
@@ -4,7 +4,6 @@
  *
  * Distributed under terms of the MIT license.
  */
-
 #ifndef R3_GVC_H
 #define R3_GVC_H
 
diff --git a/src/gvc.c b/src/gvc.c
index 5a9bcca..86ccb67 100644
--- a/src/gvc.c
+++ b/src/gvc.c
@@ -12,7 +12,7 @@
 #include "r3_gvc.h"
 
 
-char * node_id_str(int id) {
+static char * node_id_str(int id) {
     char * name = malloc(sizeof(char) * 20);
     sprintf(name, "#%d", id);
     return name;
@@ -30,12 +30,10 @@ void r3_tree_build_ag_nodes(Agraph_t * g, Agnode_t * ag_parent_node, node * n, i
         agn_child = agnode(g, node_id_str(node_cnt) , 1);
         agn_edge = agedge(g, ag_parent_node, agn_child, 0, 1);
         agsafeset(agn_edge, "label", e->pattern, "");
-
+        if (e->child && e->child->endpoint) {
+            agsafeset(agn_child, "shape", "doublecircle", "");
+        }
         r3_tree_build_ag_nodes(g, agn_child, e->child, node_cnt);
-
-        // agedgeattr(agn_edge, "label", e->pattern );
-        // agattr(gr, AGEDGE, "style","invis");
-        // agattr(agn_edge, AGEDGE, "label", "test");
     }
 }
 
diff --git a/tests/bench_str.csv b/tests/bench_str.csv
index d2601b5..f42892a 100644
--- a/tests/bench_str.csv
+++ b/tests/bench_str.csv
@@ -391,3 +391,5 @@
 1400600045,13977543.80
 1400600057,13901438.41
 1400600326,14049707.03
+1400600677,13384789.38
+1400600754,13649118.34