aga,agar: New shortcut2 sample graph and testcases based on it

This patch adds a new test graph "shortcut2" which includes a negative cost
edge.  Along with that we add a testcase for Dijkstra's algorithm checking
that it gracefully fails in this case.

Signed-off-by: David Gibson <david@gibson.dropbear.id.au>

ccan/aga/test/api-adjacency.c

@@ -62,8 +62,9 @@ int main(void)
 	struct error_graph eg;
 	struct traversal1_graph t1g;
 	struct shortcut1_graph s1g;
+	struct shortcut2_graph s2g;
 
-	plan_tests(2 + 7 + 35 + 30 + 30 + 42 + 9 + 30 + 9);
+	plan_tests(2 + 7 + 35 + 30 + 30 + 42 + 9 + 30 + 9 + 9);
 
 	trivial_graph_init(&tg);
 	test_adjacency("trivial", &tg.sg, trivial_adjacency);
@@ -95,5 +96,8 @@ int main(void)
 	shortcut1_graph_init(&s1g);
 	test_adjacency("shortcut1 graph", &s1g.sg, shortcut1_adjacency);
 
+	shortcut2_graph_init(&s2g);
+	test_adjacency("shortcut2 graph", &s2g.sg, shortcut2_adjacency);
+
 	return exit_status();
 }

ccan/aga/test/api-dijkstra.c

@@ -234,12 +234,24 @@ static void test_shortcut1(void)
 	aga_finish(&s1g.sg.g);
 }
 
+static void test_shortcut2(void)
+{
+	struct shortcut2_graph s2g;
+
+	shortcut2_graph_init(&s2g);
+
+	ok1(aga_dijkstra_start(&s2g.sg.g, &s2g.sg.nodes[1]) == 0);
+	aga_dijkstra_all_paths(&s2g.sg.g);
+	ok1(aga_error(&s2g.sg.g) == AGA_ERR_NEGATIVE_COST);
+	aga_finish(&s2g.sg.g);
+}
+
 int main(void)
 {
 	plan_tests(7 + 20
 		   + FULL_LEN * (1 + FULL_LEN*4)
 		   + CHAIN_LEN * (1 + CHAIN_LEN*2)
-		   + 12 + 32 + 7);
+		   + 12 + 32 + 7 + 2);
 
 	test_trivial();
 	test_parallel();
@@ -248,6 +260,7 @@ int main(void)
 	test_error();
 	test_traversal1();
 	test_shortcut1();
+	test_shortcut2();
 	
 	return exit_status();
 }

ccan/aga/test/shortcut2.c

@@ -0,0 +1,94 @@
+#include "config.h"
+
+#include <assert.h>
+
+#include <ccan/container_of/container_of.h>
+#include <ccan/ptrint/ptrint.h>
+
+#include <ccan/aga/aga.h>
+
+#include "simple-graph.h"
+
+static ptrint_t *shortcut2_first_edge(const struct aga_graph *g,
+				      const struct aga_node *n)
+{
+	struct shortcut2_graph *s1g = container_of(g, struct shortcut2_graph,
+						   sg.g);
+	int ni = n - s1g->sg.nodes;
+
+	switch (ni) {
+	case 1:
+	case 2:
+		return int2ptr(1);
+
+	case 3:
+		return NULL;
+
+	default:
+		assert(0);
+	}
+}
+
+static ptrint_t *shortcut2_next_edge(const struct aga_graph *g,
+				     const struct aga_node *n,
+				     ptrint_t *e)
+{
+	struct shortcut2_graph *s1g = container_of(g, struct shortcut2_graph,
+						   sg.g);
+	int ni = n - s1g->sg.nodes;
+	int index = ptr2int(e);
+
+	switch (ni) {
+	case 1:
+		if (index == 1)
+			return int2ptr(2);
+		assert(index == 2);
+		return NULL;
+
+	case 2:
+		assert(index == 1);
+		return NULL;
+
+	default:
+		assert(0);
+	}
+}
+
+static int shortcut2_edge_info(const struct aga_graph *g,
+			       const struct aga_node *n,
+			       ptrint_t *e, struct aga_edge_info *ei)
+{
+	struct shortcut2_graph *s1g = container_of(g, struct shortcut2_graph,
+						   sg.g);
+	int ni = n - s1g->sg.nodes;
+	int index = ptr2int(e);
+
+	switch (ni) {
+	case 1:
+		if (index == 1) {
+			ei->to = &s1g->sg.nodes[3];
+		} else {
+			assert(index == 2);
+			ei->to = &s1g->sg.nodes[2];
+		}
+		ei->icost = 2;
+		break;
+
+	case 2:
+		assert(index == 1);
+		ei->to = &s1g->sg.nodes[3];
+		ei->icost = -1;
+		break;
+
+	default:
+		assert(0);
+	}
+	return 0;
+}
+
+void shortcut2_graph_init(struct shortcut2_graph *s1g)
+{
+	simple_graph_init(&s1g->sg, shortcut2_first_edge,
+			  shortcut2_next_edge,
+			  shortcut2_edge_info);
+}

ccan/aga/test/simple-graph.h

@@ -235,4 +235,25 @@ static const struct adjacency_list shortcut1_adjacency[] = {
 	{},
 };
 
+/* Shortcut-2 graph
+ *
+ *   A ---- (2) -----> C
+ *    \             /
+ *     (2)-> B  --(-1)
+ *
+ * This provides an example of a graph with a negative edge cost, but
+ * no negative cost cycles (and so still with well defined shortest
+ * paths).
+ */
+struct shortcut2_graph {
+	struct simple_graph sg;
+};
+void shortcut2_graph_init(struct shortcut2_graph *s2g);
+static const struct adjacency_list shortcut2_adjacency[] = {
+	{1, {3, 2}},
+	{2, {3}},
+	{3, {}},
+	{},
+};
+
 #endif /* _TEST_GRAPHS_H */

ccan/agar/test/api-adjacency.c

@@ -56,8 +56,9 @@ int main(void)
 	struct grid_graphr ggr1, ggr2;
 	struct error_graphr egr;
 	struct shortcut1_graphr s1gr;
+	struct shortcut2_graphr s2gr;
 
-	plan_tests(1 + 5 + 30 + 22 + 21 + 33 + 6 + 6);
+	plan_tests(1 + 5 + 30 + 22 + 21 + 33 + 6 + 6 + 6);
 
 	trivial_graphr_init(&tgr);
 	test_adjacency("trivial", &tgr.gr, trivial_adjacencyr);
@@ -86,5 +87,8 @@ int main(void)
 	shortcut1_graphr_init(&s1gr);
 	test_adjacency("shortcut1 graph", &s1gr.gr, shortcut1_adjacencyr);
 
+	shortcut2_graphr_init(&s2gr);
+	test_adjacency("shortcut2 graph", &s2gr.gr, shortcut2_adjacencyr);
+	
 	return exit_status();
 }

ccan/agar/test/api-dijkstra.c

@@ -238,12 +238,25 @@ static void test_shortcut1(void)
 	tal_free(sr);
 }
 
+static void test_shortcut2(void)
+{
+	struct shortcut2_graphr s2gr;
+	struct agar_state *sr;
+
+	shortcut2_graphr_init(&s2gr);
+
+	ok1(sr = agar_dijkstra_new(NULL, &s2gr.gr, int2ptr(1)));
+	agar_dijkstra_all_paths(sr);
+	ok1(agar_error(sr) == AGA_ERR_NEGATIVE_COST);
+	tal_free(sr);
+}
+
 int main(void)
 {
 	plan_tests(6 + 23
 		   + FULL_LEN * (FULL_LEN*4 - 1)
 		   + CHAIN_LEN * (1 + CHAIN_LEN*2)
-		   + 12 + 32 + 7);
+		   + 12 + 32 + 7 + 2);
 
 	test_trivial();
 	test_parallel();
@@ -252,6 +265,7 @@ int main(void)
 	test_error();
 	test_traversal1();
 	test_shortcut1();
+	test_shortcut2();
 	
 	return exit_status();
 }

ccan/agar/test/shortcut2.c

@@ -0,0 +1,87 @@
+#include "config.h"
+
+#include <assert.h>
+
+#include <ccan/container_of/container_of.h>
+#include <ccan/ptrint/ptrint.h>
+
+#include <ccan/agar/agar.h>
+
+#include "simple-graphr.h"
+
+static const void *shortcut2_first_edge_r(const struct agar_graph *gr,
+					  const void *nr)
+{
+	int ni = ptr2int(nr);
+
+	switch (ni) {
+	case 1:
+	case 2:
+		return int2ptr(1);
+
+	case 3:
+		return NULL;
+
+	default:
+		assert(0);
+	}
+}
+
+static const void *shortcut2_next_edge_r(const struct agar_graph *gr,
+					 const void *nr, const void *e)
+{
+	int ni = ptr2int(nr);
+	int index = ptr2int(e);
+
+	switch (ni) {
+	case 1:
+		if (index == 1)
+			return int2ptr(2);
+		assert(index == 2);
+		return NULL;
+
+	case 2:
+		assert(index == 1);
+		return NULL;
+
+	default:
+		assert(0);
+	}
+}
+
+static int shortcut2_edge_info_r(const struct agar_graph *gr,
+				 const void *nr, const void *e,
+				 struct agar_edge_info *eir)
+{
+	int ni = ptr2int(nr);
+	int index = ptr2int(e);
+
+	switch (ni) {
+	case 1:
+		if (index == 1) {
+			eir->to = int2ptr(3);
+		} else {
+			assert(index == 2);
+			eir->to = int2ptr(2);
+		}
+		eir->icost = 2;
+		break;
+
+	case 2:
+		assert(index == 1);
+		eir->to = int2ptr(3);
+		eir->icost = -1;
+		break;
+
+	default:
+		assert(0);
+	}
+	return 0;
+}
+
+void shortcut2_graphr_init(struct shortcut2_graphr *s1gr)
+{
+	agar_init_graph(&s1gr->gr, shortcut2_first_edge_r,
+			shortcut2_next_edge_r,
+			shortcut2_edge_info_r);
+}

ccan/agar/test/simple-graphr.h

@@ -219,4 +219,25 @@ static const struct adjacency_listr shortcut1_adjacencyr[] = {
 	{},
 };
 
+/* Shortcut-2 graph
+ *
+ *   A ---- (2) -----> C
+ *    \             /
+ *     (2)-> B  --(-1)
+ *
+ * This provides an example of a graph with a negative edge cost, but
+ * no negative cost cycles (and so still with well defined shortest
+ * paths).
+ */
+struct shortcut2_graphr {
+	struct agar_graph gr;
+};
+void shortcut2_graphr_init(struct shortcut2_graphr *s2gr);
+static const struct adjacency_listr shortcut2_adjacencyr[] = {
+	{1, {3, 2}},
+	{2, {3}},
+	{3, {}},
+	{},
+};
+
 #endif /* _SIMPLE_GRAPHR_H */