From c10777a245510e95329dd020f6567ce26aa60f41 Mon Sep 17 00:00:00 2001
From: Rowan Cockett <rowan@3ptscience.com>
Date: Tue, 16 Feb 2016 22:00:12 -0800
Subject: [PATCH] Addition of unitCellGrad. Possibly rename to cellGradStencil?

---
 SimPEG/Mesh/DiffOperators.py | 50 ++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/SimPEG/Mesh/DiffOperators.py b/SimPEG/Mesh/DiffOperators.py
index 00bf0259..22b87edd 100644
--- a/SimPEG/Mesh/DiffOperators.py
+++ b/SimPEG/Mesh/DiffOperators.py
@@ -565,6 +565,56 @@ class DiffOperators(object):
 
         return Pbc, Pin, Pout
 
+    def unitCellGradx():
+        doc = """Cell centered Gradient in the x dimension used for
+                regularization. The gradient operator is square (nC-by-nC)"""
+        def fget(self):
+            if self.dim < 3: return None
+            if getattr(self, '_unitCellGradx', None) is None:
+
+                n = self.vnC
+                gx = ddx(n[0]-1)
+                gx_square = sp.vstack((gx,gx[-1,:]*-1), format="csr")
+
+                self._unitCellGradx = kron3(speye(n[2]), speye(n[1]), gx_square)
+
+            return self._unitCellGradx
+        return locals()
+    unitCellGradx = property(**unitCellGradx())
+
+    def unitCellGrady():
+        doc = """Cell centered Gradient in they dimension used for
+                regularization. The gradient operator is square (nC-by-nC)"""
+        def fget(self):
+            if self.dim < 3: return None
+            if getattr(self, '_unitCellGrady', None) is None:
+
+                n = self.vnC
+                gy = ddx(n[1]-1)
+                gy_square = sp.vstack((gy,gy[-1,:]*-1), format="csr")
+
+                self._unitCellGrady = kron3(speye(n[2]), gy_square, speye(n[0]))
+
+            return self._unitCellGrady
+        return locals()
+    unitCellGrady = property(**unitCellGrady())
+
+    def unitCellGradz():
+        doc = """Cell centered Gradient in they dimension used for
+                regularization. The gradient operator is square (nC-by-nC)"""
+        def fget(self):
+            if self.dim < 3: return None
+            if getattr(self, '_unitCellGradz', None) is None:
+
+                n = self.vnC
+                gz = ddx(n[2]-1)
+                gz_square = sp.vstack((gz,gz[-1,:]*-1), format="csr")
+
+                self._unitCellGradz = kron3( gz_square , speye(n[1]), speye(n[0]))
+
+            return self._unitCellGradz
+        return locals()
+    unitCellGradz = property(**unitCellGradz())
 
     # --------------- Averaging ---------------------