fix invocation of curvature tests; provide some missing MultiField functionality

nifty5/library/gaussian_energy.py

@@ -61,4 +61,6 @@ class GaussianEnergy(Energy):
     @property
     @memo
     def curvature(self):
+        if self._cov is None:
+            return SandwichOperator.make(self._inp.gradient, None)
         return SandwichOperator.make(self._inp.gradient, self._cov.inverse)

nifty5/multi/multi_field.py

@@ -164,10 +164,25 @@ class MultiField(object):
     def __neg__(self):
         return MultiField({key: -val for key, val in self.items()})
 
+    def __abs__(self):
+        return MultiField({key: abs(val) for key, val in self.items()})
+
     def conjugate(self):
         return MultiField({key: sub_field.conjugate()
                            for key, sub_field in self.items()})
 
+    def all(self):
+        for v in self.values():
+            if not v.all():
+                return False
+        return True
+
+    def any(self):
+        for v in self.values():
+            if v.any():
+                return True
+        return False
+
     def isEquivalentTo(self, other):
         """Determines (as quickly as possible) whether `self`'s content is
         identical to `other`'s content."""

test/test_energies/test_map.py

@@ -93,7 +93,7 @@ class Energy_Tests(unittest.TestCase):
             N = None
 
         energy = ift.GaussianEnergy(d_model, d, N)
-        if isinstance(nonlinearity, ift.Linear):
+        if isinstance(nonlinearity(), ift.Linear):
             ift.extra.check_value_gradient_curvature_consistency(
                 energy, ntries=10)
         else: