df_dmT + du_dmT has dtype('o')

This seems making problem depending on which machine you are using .... or numpy version. 

We may need to clarify what is sparse and dense for arrays!!

SimPEG/EM/Static/DC/ProblemDC_2D.py

@@ -83,7 +83,7 @@ class BaseDCProblem_2D(BaseEMProblem):
         if not isinstance(v, self.dataPair):
             v = self.dataPair(self.survey, v)
 
-        Jtv = np.zeros(m.size)
+        Jtv = np.zeros(m.size, dtype=float)
 
         # Assume y=0.
         # This needs some thoughts to implement in general when src is dipole
@@ -93,8 +93,8 @@ class BaseDCProblem_2D(BaseEMProblem):
 
         for src in self.survey.srcList:
             for rx in src.rxList:
-                Jtv_temp1 = np.zeros(m.size)
-                Jtv_temp0 = np.zeros(m.size)
+                Jtv_temp1 = np.zeros(m.size, dtype=float)
+                Jtv_temp0 = np.zeros(m.size, dtype=float)
                 #TODO: this loop is pretty slow .. (Parellize)
                 for iky in range(self.nky):
                     u_src = f[src, self._solutionType, iky]
@@ -109,7 +109,7 @@ class BaseDCProblem_2D(BaseEMProblem):
                     dA_dmT = self.getADeriv(ky, u_src, ATinvdf_duT, adjoint=True)
                     dRHS_dmT = self.getRHSDeriv(ky, src, ATinvdf_duT, adjoint=True)
                     du_dmT = -dA_dmT + dRHS_dmT
-                    Jtv_temp1 = 1./np.pi*(df_dmT + du_dmT)
+                    Jtv_temp1 = 1./np.pi*(df_dmT + du_dmT).astype(float)
                     # Trapezoidal intergration
                     if iky==0:
                         #First assigment