diff --git a/CONTRIBUTING.rst b/CONTRIBUTING.rst
index 888a114b..ff0a9c50 100644
--- a/CONTRIBUTING.rst
+++ b/CONTRIBUTING.rst
@@ -49,7 +49,7 @@ To run all tests with unittest, execute
 
 .. code-block:: shell
 
-    python -m unittest discover test
+    python -m unittest discover tests
 
 To generate coverage reports, execute
 
diff --git a/docs/conf.py b/docs/conf.py
index 0617e93b..48f3f8ff 100644
--- a/docs/conf.py
+++ b/docs/conf.py
@@ -25,9 +25,9 @@
 author = u'Author'
 
 # The short X.Y version
-version = u'0.1'
+version = u'1.0'
 # The full version, including alpha/beta/rc tags
-release = u'0.0.1'
+release = u'1.0.5'
 
 
 # -- General configuration ---------------------------------------------------
diff --git a/pyqubo/integer/integer.py b/pyqubo/integer/integer.py
index 2dc5a469..8e0e6cb3 100644
--- a/pyqubo/integer/integer.py
+++ b/pyqubo/integer/integer.py
@@ -13,7 +13,6 @@
 # limitations under the License.
 
 import abc
-import six
 from cpp_pyqubo import UserDefinedExpress, WithPenalty
 
 
diff --git a/pyqubo/package_info.py b/pyqubo/package_info.py
index d4a763e6..c0105bac 100644
--- a/pyqubo/package_info.py
+++ b/pyqubo/package_info.py
@@ -1,6 +1,6 @@
 # (major, minor, patch, prerelease)
 
-VERSION = (1, 0, 4, "")
+VERSION = (1, 0, 5, "")
 __shortversion__ = '.'.join(map(str, VERSION[:3]))
 __version__ = '.'.join(map(str, VERSION[:3])) + "".join(VERSION[3:])
 
diff --git a/setup.py b/setup.py
index 6f1d41e7..564952c1 100644
--- a/setup.py
+++ b/setup.py
@@ -104,7 +104,8 @@ def run(self):
     'numpy>=1.16.0,<2.0.0',
     'dimod>=0.9.2',
     'dwave-neal>=0.5.4',
-    'Deprecated>=1.2.10'
+    'Deprecated>=1.2.10',
+    'six>=1.11.0'
     ]
 
 python_requires = '>=3.5'
diff --git a/src/reduce_order.cpp b/src/reduce_order.cpp
index 7864cc88..1f178c4b 100644
--- a/src/reduce_order.cpp
+++ b/src/reduce_order.cpp
@@ -10,11 +10,8 @@ namespace reduce_order{
         void add_term(Terms* terms, Prod prod, CoeffPtr coeff){
             auto result = terms->find(prod);
             if(result == terms->end()){
-                //terms->at(prod) = coeff;
                 terms->insert(TermsPair{prod, coeff});
             }else{
-                //terms->at(prod) = coeff->add(result->second);
-                //terms->insert(TermsPair{prod, coeff->add(result->second)});
                 result->second = coeff->add(result->second);
             }
         }
@@ -71,9 +68,7 @@ namespace reduce_order{
         }
 
         void replace_variable(Poly* mp, QuboIndex index_pair, int new_variable){
-            int loop_cnt = 0;
             for(auto it = mp->terms->begin(); it != mp->terms->end(); it++){
-                loop_cnt++;
                 Prod prod = it->first;
                 CoeffPtr coeff = it->second;
                 bool first_in, second_in = false;
@@ -82,7 +77,7 @@ namespace reduce_order{
                     if(prod.get_var(i) == index_pair.second) second_in = true;
                 }
                 if(first_in && second_in){
-                    uint32_t indices[4] = {0};
+                    uint32_t* indices = new uint32_t[it->first.length+1];
                     int index = 0;
                     for(int i=0; i < it->first.length; i++){
                         if(prod.get_var(i) != index_pair.first && prod.get_var(i) != index_pair.second){
diff --git a/tests/_test_main.py b/tests/_test_main.py
deleted file mode 100644
index b82dc736..00000000
--- a/tests/_test_main.py
+++ /dev/null
@@ -1,89 +0,0 @@
-from pyqubo import Binary, Add, Num, Mul, Dog, DogAdd, WithPenalty, SubH
-#from pyqubo import Binary, Add, Num, Mul
-import unittest
-import time
-#from memory_profiler import profile
-#from memory_profiler import memory_usage
-import gc
-import sys
-from copy import copy
-
-
-class TestExpressEquality(unittest.TestCase):
-    
-    def test_main3(self):
-        t0 = time.time()
-        n = 40
-        H = Binary("a")
-        for i in range(n):
-            a = Binary("a")
-            for j in range(n):
-                b = Binary(f"b_{i}_{j}")
-                a = a + b
-            H = Add(H, Mul(a, a))
-        
-        for j in range(n):
-            a = Binary("a")
-            for i in range(n):
-                b = Binary(f"b_{i}_{j}")
-                a = a + b
-            H = Add(H, Mul(a, a))
-
-        for i in range(n):
-            for j in range(n):
-                for k in range(n):
-                    b1 = Binary(f"b_{i}_{j}")
-                    b2 = Binary(f"b_{j}_{k}")
-                    H = H + b1*b2
-
-        model = H.compile(1.0)
-        t1 = time.time()
-        print("compile:", t1-t0)
-        qubo, offset = model.to_qubo(False, {})
-        #print(qubo, offset)
-        t2 = time.time()
-        print(t2-t1)
-    
-    def _test_main2(self):
-        class CustomPenalty(WithPenalty):
-            def __init__(self):
-                WithPenalty.__init__(self)
-                self.hamiltonian = Binary("a")
-                self.penalty = Binary("b")
-
-        custom_penalty = CustomPenalty()
-        print(custom_penalty)
-    
-    def _test_main1(self):
-        pass
-        array_index = ArrayIndex("b", "array_name", (2, 2), [0, 0])
-        a = Binary("a", array_index)
-        array_index2 = ArrayIndex("b", "array_name", [2, 2], [0, 1])
-        b = Binary("b", array_index2)
-        model = (a+b).compile(1.0)
-        print(model)
-    
-    def _test_main4(self):
-        array_index = ArrayIndex("b", "array_name", [2, 2], [0, 0])
-        h = Binary("b", array_index)
-        subh = SubH(h, "label1")
-        H = subh+Binary("a")
-        model = H.compile(1)
-        print(model)
-        sol = model.decode_solutions([{"a": 1, "b": 1}], "BINARY", {})
-        array = sol[0].arrays["array_name"]
-        print("array.keys()", array.keys())
-        print("array[0,0]", array[0, 0])
-
-        class Sample:
-            def __init__(self):
-                pass
-            def __getitem__(self, key):
-                print(key)
-        s = Sample()
-        print(s[0])
-        print(s[0:10])
-        print(s[0:1,:])
-
-if __name__ == '__main__':
-    unittest.main()
diff --git a/tests/test_express.py b/tests/test_express.py
index 791e14f7..284c9635 100644
--- a/tests/test_express.py
+++ b/tests/test_express.py
@@ -106,7 +106,6 @@ def test_compile_subh(self):
         self.compile_check(exp, expected_qubo, expected_offset, feed_dict)
     
     def test_compile_constraint(self):
-        import dimod
         a, b, c = Binary("a"), Binary("b"), Binary("c")
         exp = Constraint(a*b*c, label="constraint")
         expected_qubo = {('a', '0*1'): -10.0, ('b', '0*1'): -10.0, ('0*1', '0*1'): 15.0, ('a', 'a'): 0.0, ('a', 'b'): 5.0, ('c', '0*1'): 1.0, ('b', 'b'): 0.0, ('c', 'c'): 0.0}
@@ -126,6 +125,6 @@ def __init__(self, hamiltonian, penalty, label):
         expected_offset = 0.0
         feed_dict={"p": 2}
         self.compile_check(custom_penalty, expected_qubo, expected_offset, feed_dict)
-
+    
 if __name__ == '__main__':
     unittest.main()
diff --git a/tests/test_model.py b/tests/test_model.py
index 85182f18..536df3cd 100644
--- a/tests/test_model.py
+++ b/tests/test_model.py
@@ -236,6 +236,22 @@ def test_constraint(self):
             if sol.energy==1.0:
                 self.assertEqual(sol.subh['C1'], 1.0)
         
+    def test_higher_order(self):
+        x = Array.create('x', 5, 'BINARY')
+        exp = x[0]*x[1]*x[2]*x[3]
+        model = exp.compile(strength=10)
+
+        sample = {'x[0]': 1, 'x[1]': 1, 'x[2]': 1, 'x[3]': 1, '0*1': 1, '2*3': 1}
+        e = model.energy(sample, vartype='BINARY')
+        self.assertEqual(e, 1.0)
+
+        sample = {'x[0]': 0, 'x[1]': 1, 'x[2]': 1, 'x[3]': 1, '0*1': 0, '2*3': 1}
+        e = model.energy(sample, vartype='BINARY')
+        self.assertEqual(e, 0.0)
+        
+        sample = {'x[0]': 1, 'x[1]': 1, 'x[2]': 1, 'x[3]': 1, '0*1': 0, '2*3': 1}
+        e = model.energy(sample, vartype='BINARY')
+        self.assertEqual(e, 10.0)
 
 if __name__ == '__main__':
     unittest.main()