try using list for Jv instead of datapair - has been seen to cause memory leaks

SimPEG/EM/FDEM/ProblemFDEM.py

@@ -74,7 +74,8 @@ class BaseFDEMProblem(BaseEMProblem):
 
         self.curModel = m
 
-        Jv = self.dataPair(self.survey)
+        # Jv = self.dataPair(self.survey)
+        Jv = []
 
         for freq in self.survey.freqs:
             A = self.getA(freq)
@@ -89,9 +90,9 @@ class BaseFDEMProblem(BaseEMProblem):
                 for rx in src.rxList:
                     df_dmFun = getattr(f, '_{0}Deriv'.format(rx.projField), None)
                     df_dm_v = df_dmFun(src, du_dm_v, v, adjoint=False)
-                    Jv[src, rx] = rx.evalDeriv(src, self.mesh, f, df_dm_v)
+                    Jv.append(rx.evalDeriv(src, self.mesh, f, df_dm_v))
             Ainv.clean()
-        return Utils.mkvc(Jv)
+        return np.hstack(Jv)
 
     def Jtvec(self, m, v, f=None):
         """