Minor changes...test runs fine from here

SimPEG/Directives.py

@@ -271,7 +271,8 @@ class Update_IRLS(InversionDirective):
 
         self.reg.curModel = self.invProb.curModel
         self.reg.gamma = self.gamma
-
+        
+        self.reg._W = None
         if getattr(self, 'phi_d_last', None) is None:
             self.phi_d_last = self.invProb.phi_d
 
@@ -287,7 +288,8 @@ class Update_IRLS(InversionDirective):
 
         # Get phi_m at the end of current iteration
         self.phi_m_last = self.invProb.phi_m_last
-
+        
+        self.reg._W = None
          # Update the model used for the IRLS weights
         self.reg.curModel = self.invProb.curModel
 
@@ -296,10 +298,10 @@ class Update_IRLS(InversionDirective):
 
         # Compute new model objective function value
         phim_new = self.reg.eval(self.invProb.curModel)
-
+        
         # Update gamma to scale the regularization between IRLS iterations
         self.reg.gamma = self.phi_m_last / phim_new
-
+        
         # Set the weighting matrix to None so that it is recomputed next time
         # it is called in the inversion
         self.reg._W = None

SimPEG/Regularization.py

@@ -665,7 +665,6 @@ class Sparse(Simple):
         else:
             f_m = self.mapping * (self.curModel - self.reg.mref)
             self.rs = self.R(f_m , self.eps_p, self.norms[0])
-            #print "Min rs: " + str(np.max(self.rs)) + "Max rs: " + str(np.min(self.rs))
             self.Rs = Utils.sdiag( self.rs )
 
         return Utils.sdiag((self.regmesh.vol*self.alpha_s*self.gamma*self.wght)**0.5)*self.Rs
@@ -729,6 +728,7 @@ class Sparse(Simple):
     def W(self):
         """Full regularization matrix W"""
         if getattr(self, '_W', None) is None:
+    
             wlist = (self.Wsmall, self.Wsmooth)
             self._W = sp.vstack(wlist)
         return self._W