Minor tweaks

mitxgraders/matrixsampling.py

@@ -93,7 +93,6 @@ class ArraySamplingSet(VariableSamplingSet):
     True
 
     """
-
     schema_config = Schema({
         Required('shape'): is_shape_specification(min_dim=1),
         Required('norm', default=[1, 5]): NumberRange(),
@@ -109,12 +108,12 @@ def __init__(self, config=None, **kwargs):
 
     def gen_sample(self):
         """
-        Generates a random matrix of shape and norm determined by config.
-
-        After generation, subclasses can modify the result by shadowing the
-        apply_symmetry function.
+        Generates a random matrix of shape and norm determined by config. After
+        generation, the apply_symmetry and normalize functions are applied to the result.
+        These functions may be shadowed by a subclass.
 
-        After apply_symmetry is called, the result is normalized.
+        If apply_symmetry or normalize raise the Retry exception, a new sample is
+        generated, and the procedure starts anew.
         """
         # Loop until a good sample is found
         loops = 0
@@ -137,8 +136,8 @@ def gen_sample(self):
 
                 # Convert the array to a MathArray and return it
                 return MathArray(array)
-            except Retry:  # pragma: no cover
-                pass
+            except Retry:
+                continue
 
         raise ValueError('Unable to construct sample for {}'
                          .format(self.__name__))  # pragma: no cover
@@ -545,6 +544,13 @@ def __init__(self, config=None, **kwargs):
         if self.config['symmetry'] in ['hermitian', 'antihermitian']:
             self.config['complex'] = True
 
+        # A couple of cases that we can't handle:
+        if self.config['determinant'] == 0:
+            if self.config['symmetry'] == 'antisymmetric':
+                raise ConfigError("Unable to generate zero determinant antisymmetric matrices")
+            if self.config['traceless']:
+                raise ConfigError("Unable to generate zero determinant traceless matrices")
+
     def apply_symmetry(self, array):
         """
         Applies the required symmetries to the array
@@ -612,7 +618,7 @@ def make_det_one(self, array):
                 raise Retry()
 
             # If we get to here, det is real
-            det = np.real(det)
+            det = np.real(det)  # Get rid of numerical error
             if det > 0:
                 # This is the easy case: Just scale the determinant
                 return array / np.power(det, 1/self.config['dimension'])
@@ -630,12 +636,6 @@ def make_det_zero(self, array):
             # This should never happen due to floating pointness. But just in case...
             return array  # pragma: no cover
 
-        # A couple of cases that we just can't handle:
-        if self.config['symmetry'] == 'antisymmetric':
-            raise ConfigError("Unable to generate zero determinant antisymmetric matrices")
-        if self.config['traceless']:
-            raise ConfigError("Unable to generate zero determinant traceless matrices")
-
         # Pick a random number!
         index = np.random.randint(self.config['dimension'])