diff --git a/lib/spack/spack/solver/asp.py b/lib/spack/spack/solver/asp.py
index 3730bc6e38..f26a83f9e2 100644
--- a/lib/spack/spack/solver/asp.py
+++ b/lib/spack/spack/solver/asp.py
@@ -95,7 +95,7 @@ def default_clingo_control():
     control = clingo().Control()
     control.configuration.configuration = "tweety"
     control.configuration.solver.heuristic = "Domain"
-    control.configuration.solver.opt_strategy = "usc,one,1"
+    control.configuration.solver.opt_strategy = "usc,one"
     return control
 
 
diff --git a/lib/spack/spack/solver/heuristic.lp b/lib/spack/spack/solver/heuristic.lp
index 1f31d7eae0..a5d6767ff2 100644
--- a/lib/spack/spack/solver/heuristic.lp
+++ b/lib/spack/spack/solver/heuristic.lp
@@ -8,13 +8,17 @@
 %=============================================================================
 
 % No duplicates by default (most of them will be true)
-#heuristic attr("node",         node(1..X-1, Package)) : max_dupes(Package, X), not virtual(Package), X > 1. [100, false]
-#heuristic attr("virtual_node", node(1..X-1, Package)) : max_dupes(Package, X), virtual(Package)    , X > 1. [100, false]
+#heuristic attr("node",         node(PackageID, Package)). [100, init]
+#heuristic attr("node",         node(PackageID, Package)). [  2, factor]
+#heuristic attr("virtual_node", node(VirtualID, Virtual)). [100, init]
+#heuristic attr("node",         node(1..X-1, Package)) : max_dupes(Package, X), not virtual(Package), X > 1. [-1, sign]
+#heuristic attr("virtual_node", node(1..X-1, Package)) : max_dupes(Package, X), virtual(Package)    , X > 1. [-1, sign]
 
 % Pick preferred version
-#heuristic attr("version", node(PackageID, Package), Version) : pkg_fact(Package, version_declared(Version, 0     )), attr("node", node(PackageID, Package)).             [40, true]
-#heuristic attr("version", node(PackageID, Package), Version) : pkg_fact(Package, version_declared(Version, Weight)), attr("node", node(PackageID, Package)), Weight > 0. [40+5*Weight, false]
-#heuristic version_weight(node(PackageID, Package), 0)        : pkg_fact(Package, version_declared(Version, 0     )), attr("node", node(PackageID, Package)).             [40, true]
+#heuristic attr("version", node(PackageID, Package), Version) : pkg_fact(Package, version_declared(Version, Weight)), attr("node", node(PackageID, Package)).             [40, init]
+#heuristic version_weight(node(PackageID, Package), 0)        : pkg_fact(Package, version_declared(Version, 0     )), attr("node", node(PackageID, Package)).             [ 1, sign]
+#heuristic attr("version", node(PackageID, Package), Version) : pkg_fact(Package, version_declared(Version, 0     )), attr("node", node(PackageID, Package)).             [ 1, sign]
+#heuristic attr("version", node(PackageID, Package), Version) : pkg_fact(Package, version_declared(Version, Weight)), attr("node", node(PackageID, Package)), Weight > 0. [-1, sign]
 
 % Use default variants
 #heuristic attr("variant_value", node(PackageID, Package), Variant, Value) : variant_default_value(Package, Variant, Value),     attr("node", node(PackageID, Package)). [40, true]
@@ -25,10 +29,10 @@
 #heuristic attr("node_platform", node(PackageID, Package), Platform) : allowed_platform(Platform), attr("root", node(PackageID, Package)). [40, true]
 
 % Use default targets
-#heuristic attr("node_target", node(PackageID, Package), Target) : target_weight(Target, 0), attr("node", node(PackageID, Package)). [30, true]
-#heuristic attr("node_target", node(PackageID, Package), Target) : target_weight(Target, Weight), attr("node", node(PackageID, Package)), Weight > 0. [30, false]
-#heuristic node_target_weight(node(PackageID, Package), 0) : attr("node", node(PackageID, Package)). [30, true]
+#heuristic attr("node_target", node(PackageID, Package), Target) : target_weight(Target, Weight), attr("node", node(PackageID, Package)). [30, init]
+#heuristic attr("node_target", node(PackageID, Package), Target) : target_weight(Target, Weight), attr("node", node(PackageID, Package)). [ 2, factor]
+#heuristic attr("node_target", node(PackageID, Package), Target) : target_weight(Target,      0), attr("node", node(PackageID, Package)). [ 1, sign]
+#heuristic attr("node_target", node(PackageID, Package), Target) : target_weight(Target, Weight), attr("node", node(PackageID, Package)), Weight > 0. [-1, sign]
 
 % Use the default compilers
-#heuristic node_compiler(node(0, Package), ID) : compiler_weight(ID, 0)     , compiler_id(ID), attr("node", node(0, Package)). [30, true]
-#heuristic node_compiler(node(0, Package), ID) : compiler_weight(ID, Weight), compiler_id(ID), attr("node", node(0, Package)), Weight > 0. [30, false]
+#heuristic node_compiler(node(PackageID, Package), ID) : compiler_weight(ID, 0), compiler_id(ID), attr("node", node(PackageID, Package)). [30, init]