Index: trunk/src/plugins/rt_topo/crbs.h
===================================================================
--- trunk/src/plugins/rt_topo/crbs.h	(revision 1446)
+++ trunk/src/plugins/rt_topo/crbs.h	(revision 1447)
@@ -63,6 +63,7 @@
 	void *first_mark, *target_mark;
 	grbs_2net_t *routing_tn;
 	int max_ripup; /* how many times are we willing to rip up a 2net (total within a layer routing) */
+	long max_hop_cnt; /* stop hopeless searches after this many hops */
 } crbs_t;
 
 int rt_topo_crbs(rtrnd_t *ctx, rt_topo_laa2rbs_t *src);
Index: trunk/src/plugins/rt_topo/crbs_route.c
===================================================================
--- trunk/src/plugins/rt_topo/crbs_route.c	(revision 1446)
+++ trunk/src/plugins/rt_topo/crbs_route.c	(revision 1447)
@@ -483,12 +483,14 @@
 	ast.get_mark = crbs_ast_get_mark;
 	ast.user_data = crbs;
 
+	crbs->max_hop_cnt = hop_cnt + crbs->grbs.all_points.length * 1000.0 * rt_topo_cfg.max_hop_mult;
+
 	cnt_grbs++;
 
-	printf(" route_net: from P%ld to P%ld (step 3_GRBS_routed_%d)\n",
+	printf(" route_net: from P%ld to P%ld (step 3_GRBS_routed_%d) max_hop %ld\n",
 		((crbs_point_t *)(ctn->cstart->data))->gpt->uid,
 		((crbs_point_t *)(ctn->cend->data))->gpt->uid,
-		cnt_grbs);
+		cnt_grbs, crbs->max_hop_cnt);
 
 	sres = usrch_a_star_start(&ast, first);
 	if (sres != USRCH_RES_SUCCESS) {
@@ -496,7 +498,12 @@
 		goto err;
 	}
 
-	while((sres = usrch_a_star_iter(&ast)) == USRCH_RES_CONTINUE) ;
+	while((sres = usrch_a_star_iter(&ast)) == USRCH_RES_CONTINUE) {
+		if (hop_cnt > crbs->max_hop_cnt) {
+			printf("  a* search fail: giving up on too many hops\n");
+			goto err;
+		}
+	}
 
 	if (sres != USRCH_RES_FOUND) {
 		printf("  a* search fail 2\n");
Index: trunk/src/plugins/rt_topo/rt_topo.c
===================================================================
--- trunk/src/plugins/rt_topo/rt_topo.c	(revision 1446)
+++ trunk/src/plugins/rt_topo/rt_topo.c	(revision 1447)
@@ -44,6 +44,8 @@
 	RTRND_CONF_COORD("via_clr",           0.20, 0.01, 10, "clearance around via copper", &rt_topo_cfg.via_clr)
 	RTRND_CONF_DOUBLE("beta",             50,   0, 100,   "via vs. wire length preference; high value = short wires, low value = less vias", &rt_topo_cfg.beta)
 	RTRND_CONF_BOOLEAN("mid_virt",        0,              "split long triangulation edges in half by inserting 0 sized virtual points; makes more routes possible but also makes tracks longer with unnecessary curves and detours", &rt_topo_cfg.beta)
+	RTRND_CONF_DOUBLE("max_hop_mult",     1,  0.1, 10000, "when to give up the search for a route on a layer; higher value means give up later", &rt_topo_cfg.max_hop_mult)
+
 /*	RTRND_CONF_BOOLEAN("octilinear",      0,              "draw 90 and 45 degree lines", &rt_topo_cfg.octilin)*/
 	RTRND_CONF_TERMINATE
 };
Index: trunk/src/plugins/rt_topo/rt_topo.h
===================================================================
--- trunk/src/plugins/rt_topo/rt_topo.h	(revision 1446)
+++ trunk/src/plugins/rt_topo/rt_topo.h	(revision 1447)
@@ -18,6 +18,7 @@
 	/* configured */
 	double wire_thick, wire_clr, via_dia, via_clr, beta;
 	int octilin, algo, mid_virt;
+	double max_hop_mult;
 
 	/* calculated */
 	double alpha, alpha2;