Remove dependency of params_shape on template_params (Issue #62)

What:
1. Turn params_shape into an abstract property
2. Use params_shape instead of template_params to compute nparams in
   BaseWavefunction
3. Use nparams in BaseWavefunction.load_cache instead of params.size
4. Move around tests
Why:
1. Every time param_shape is called, template_params needs to be
   constructed. For most wavefunctions, this is not a big problem, but
   some wavefunctions actually need to do a fair bit to obtain a
   template (e.g. APr2G). The consistency between params_shape and
   template_params will be checked implicitly through assign_params,
   which checks that the given parameters has the same shape as the
   params_shape.

Fix up BaseWavefunction.nparams

wfns/wfn/base.py

@@ -116,19 +116,7 @@ def nparams(self):
             Number of parameters.
 
         """
-        return self.template_params.size
-
-    @property
-    def params_shape(self):
-        """Return the shape of the wavefunction parameters.
-
-        Returns
-        -------
-        params_shape : tuple of int
-            Shape of the parameters.
-
-        """
-        return self.template_params.shape
+        return np.prod(self.params_shape)
 
     @property
     def spin(self):
@@ -357,7 +345,7 @@ def load_cache(self):
         if self.memory == np.inf:
             memory = None
         else:
-            memory = int((self.memory - 5*8*self.params.size) / (self.params.size + 1))
+            memory = int((self.memory - 5 * 8 * self.nparams) / (self.nparams + 1))
 
         # create function that will be cached
         @functools.lru_cache(maxsize=memory, typed=False)
@@ -453,6 +441,18 @@ def clear_cache(self, key=None):
             raise AttributeError('Given cached function does not have decorator '
                                  '`functools.lru_cache`') from error
 
+    @abc.abstractproperty
+    def params_shape(self):
+        """Return the shape of the wavefunction parameters.
+
+        Returns
+        -------
+        params_shape : tuple of int
+            Shape of the parameters.
+
+        """
+        pass
+
     @abc.abstractproperty
     def template_params(self):
         """Return the template of the parameters of the given wavefunction.
@@ -464,7 +464,7 @@ def template_params(self):
 
         Notes
         -----
-        May depend on other attributes or properties.
+        May depend on params_shape and other attributes/properties.
 
         """
         pass

wfns/wfn/test/test_base.py

@@ -13,6 +13,10 @@ def __init__(self):
     def get_overlap(self):
         pass
 
+    @property
+    def params_shape(self):
+        return (10, 10)
+
     @property
     def template_params(self):
         return np.identity(10)
@@ -124,9 +128,20 @@ def test_assign_params():
     assert not np.allclose(np.real(test.params), np.identity(10))
     assert not np.allclose(np.imag(test.params), np.zeros((10, 10)))
 
-    # FIXME: hard to test because property of a class/instance cannot be overwritten easily
-    # test.template_params = np.array([[0.0]])
-    # test.assign_params(2)
+    # for testing one line of code
+    class TempTestWavefunction(TestWavefunction):
+        @property
+        def params_shape(self):
+            return (1, 1, 1)
+
+        @property
+        def template_params(self):
+            return np.array([[[0.0]]])
+
+    test = TempTestWavefunction()
+    test.assign_dtype(complex)
+    test.assign_params(2.0)
+    assert test.params.shape == (1, 1, 1)
 
 
 def test_init():
@@ -215,12 +230,6 @@ def test_nparams():
     assert test.nparams == 100
 
 
-def test_params_shape():
-    """Test BaseWavefunction.params_shape."""
-    test = TestWavefunction()
-    assert test.params_shape == (10, 10)
-
-
 def test_spin():
     """Test BaseWavefunction.spin"""
     test = TestWavefunction()