Handling null space of A

SimPEG/EM/Static/DC/ProblemDC.py

@@ -128,6 +128,10 @@ class Problem3D_N(BaseDCProblem):
         MeSigma = self.MeSigma
         Grad = self.mesh.nodalGrad
         A = Grad.T * MeSigma * Grad
+
+        # Handling ... singularity
+        A[0,0] = A[0,0] + 1.
+
         # if self._makeASymmetric is True:
         #     return V.T * A
         return A

tests/em/static/test_DC.py

@@ -104,7 +104,7 @@ class DCProblemTestsN(unittest.TestCase):
 
     def test_misfit(self):
         derChk = lambda m: [self.survey.dpred(m), lambda mx: self.p.Jvec(self.m0, mx)]
-        passed = Tests.checkDerivative(derChk, self.m0, plotIt=False, num=3)
+        passed = Tests.checkDerivative(derChk, self.m0, plotIt=False)
         self.assertTrue(passed)
 
     def test_adjoint(self):
@@ -120,7 +120,7 @@ class DCProblemTestsN(unittest.TestCase):
 
     def test_dataObj(self):
         derChk = lambda m: [self.dmis.eval(m), self.dmis.evalDeriv(m)]
-        passed = Tests.checkDerivative(derChk, self.m0, plotIt=False, num=3)
+        passed = Tests.checkDerivative(derChk, self.m0, plotIt=False)
         self.assertTrue(passed)
 if __name__ == '__main__':
     unittest.main()