1 files changed, 17 insertions, 12 deletions

diff --git a/src/solve.c b/src/solve.c
index 39437fb..5581964 100644
--- a/src/solve.c
+++ b/src/solve.c
@@ -11,11 +11,11 @@ static bool        dfs_check_solved(DfsArg *arg);
 static bool        dfs_switch(DfsArg *arg);
 static void        dfs_niss(DfsArg *arg);
 static bool        dfs_stop(DfsArg *arg);
+static bool        dfs_useless_niss(DfsArg *arg);
 static void *      instance_thread(void *arg);
 static void        invert_branch(DfsArg *arg);
 static void        multidfs(Cube c, Trans t, Step *s, SolveOptions *opts,
                             AlgList *sols, int d);
-static bool        niss_makes_sense(DfsArg *arg);
 static bool        solvestop(int d, int op, SolveOptions *opts, AlgList *sols);
 
 /* Local functions ***********************************************************/
@@ -97,7 +97,7 @@ dfs(DfsArg *arg)
                 invert_branch(arg);
         dfs_branch(arg);
 
-        if (arg->opts->nisstype == NISS && !arg->niss && niss_makes_sense(arg))
+        if (arg->opts->nisstype == NISS && !arg->niss && !arg->step->final)
                 dfs_niss(arg);
 
         if (sw)
@@ -139,7 +139,7 @@ dfs_check_solved(DfsArg *arg)
         if (!arg->step->is_done(arg->cube))
                 return false;
 
-        if (arg->current_alg->len == arg->d) {
+        if (arg->current_alg->len == arg->d && !dfs_useless_niss(arg)) {
                 if ((arg->step->is_valid(arg->current_alg) || arg->opts->all)
                     && (!arg->step->final || !cancel_niss(arg))) {
 
@@ -233,6 +233,20 @@ dfs_switch(DfsArg *arg)
         return bi < bn;
 }
 
+static bool
+dfs_useless_niss(DfsArg *arg)
+{
+        Cube c;
+        Move m = arg->last1inv;
+
+        if (m == NULLMOVE || !arg->niss)
+                return false;
+
+        c = apply_move(inverse_move(m), arg->cube);
+
+        return arg->step->is_done(c);
+}
+
 static void *
 instance_thread(void *arg)
 {
@@ -363,15 +377,6 @@ multidfs(Cube c, Trans tr, Step *s, SolveOptions *opts, AlgList *sols, int d)
 }
 
 static bool
-niss_makes_sense(DfsArg *arg)
-{
-        Cube testcube;
-
-        testcube = apply_move(inverse_move(arg->last1), (Cube){0});
-        return arg->current_alg->len == 0 || !arg->step->is_done(testcube);
-}
-
-static bool
 solvestop(int d, int op, SolveOptions *opts, AlgList *sols)
 {
         bool opt_done, max_moves_exceeded, max_sols_exceeded;