Fix dtype handling

src/operators/energy_operators.py

@@ -154,16 +154,21 @@ class VariableCovarianceGaussianEnergy(EnergyOperator):
         self._ki = str(inverse_covariance_key)
         dom = DomainTuple.make(domain)
         self._domain = MultiDomain.make({self._kr: dom, self._ki: dom})
-        self._dt = sampling_dtype
-        _check_sampling_dtype(self._domain, sampling_dtype)
+        self._dt = {self._kr: sampling_dtype, self._ki: np.float64}
+        _check_sampling_dtype(self._domain, self._dt)
+        self._cplx = np.issubdtype(sampling_dtype, np.complexfloating)
 
     def apply(self, x):
         self._check_input(x)
         r, i = x[self._kr], x[self._ki]
-        res = 0.5*(r.vdot(r*i.real).real - i.ptw("log").sum())
+        if self._cplx:
+            res = 0.5*r.vdot(r*i.real).real - i.ptw("log").sum()
+        else:
+            res = 0.5*(r.vdot(r*i) - i.ptw("log").sum())
         if not x.want_metric:
             return res
-        met = MultiField.from_dict({self._kr: i.val, self._ki: .5*i.val**(-2)})
+        met = i.val if self._cplx else 0.5*i.val
+        met = MultiField.from_dict({self._kr: i.val, self._ki: met**(-2)})
         return res.add_metric(SamplingDtypeSetter(makeOp(met), self._dt))