diff --git a/twd_solver.py b/twd_solver.py
index add2d9cf805de09fc6ea2a8c66cf0c790d44e303..e7e33ea74873d192750b3b97a1121b8f688fcf42 100644
--- a/twd_solver.py
+++ b/twd_solver.py
@@ -48,28 +48,30 @@ def solve(params):
     if not stop_flag:
         solver.print_cnf(nodes, cnfs, filename=cnf_filepath)
 
-    solution_filepath = f'{basedir}/a.txt'
-
-    cmds = f'minisat {cnf_filepath} {solution_filepath}'.split()
-
-    proc = subprocess.Popen(
-        cmds,
-        # stderr=subprocess.PIPE,
-        # stdout=subprocess.PIPE
-    )
-
-    try:
-        # outs, errs = proc.communicate()
-        proc.communicate()
-        status = 'done'
-    except Exception as ex:
-        status = 'failed'
-    finally:
-        returncode = proc.returncode
-        # outs = outs.decode()
-        # errs = errs.decode()
-        # print(outs)
-        # print(errs)
+    returncode = 0
+    if not stop_flag:
+        solution_filepath = f'{basedir}/a.txt'
+
+        cmds = f'minisat {cnf_filepath} {solution_filepath}'.split()
+
+        proc = subprocess.Popen(
+            cmds,
+            # stderr=subprocess.PIPE,
+            # stdout=subprocess.PIPE
+        )
+
+        try:
+            # outs, errs = proc.communicate()
+            proc.communicate()
+            status = 'done'
+        except Exception as ex:
+            status = 'failed'
+        finally:
+            returncode = proc.returncode
+            # outs = outs.decode()
+            # errs = errs.decode()
+            # print(outs)
+            # print(errs)
 
     solution = ''
     if returncode == 10:    # 10 when SAT