Index: /issm/trunk-jpl/src/c/Makefile.am
===================================================================
--- /issm/trunk-jpl/src/c/Makefile.am	(revision 18824)
+++ /issm/trunk-jpl/src/c/Makefile.am	(revision 18825)
@@ -407,4 +407,6 @@
 					./modules/RheologyBbarAbsGradientx/RheologyBbarAbsGradientx.cpp\
 					./modules/RheologyBbarAbsGradientx/RheologyBbarAbsGradientx.h\
+					./modules/RheologyBAbsGradientx/RheologyBAbsGradientx.cpp\
+					./modules/RheologyBAbsGradientx/RheologyBAbsGradientx.h\
 					./classes/Inputs/ControlInput.h\
 					./classes/Inputs/ControlInput.cpp\
Index: /issm/trunk-jpl/src/c/modules/RheologyBAbsGradientx/RheologyBAbsGradientx.cpp
===================================================================
--- /issm/trunk-jpl/src/c/modules/RheologyBAbsGradientx/RheologyBAbsGradientx.cpp	(revision 18825)
+++ /issm/trunk-jpl/src/c/modules/RheologyBAbsGradientx/RheologyBAbsGradientx.cpp	(revision 18825)
@@ -0,0 +1,79 @@
+/*!\file RheologyBAbsGradientx
+ * \brief: compute misfit between observations and model
+ */
+
+#include "./RheologyBAbsGradientx.h"
+
+#include "../../shared/shared.h"
+#include "../../toolkits/toolkits.h"
+
+void RheologyBAbsGradientx( IssmDouble* pJ, Elements* elements,Nodes* nodes, Vertices* vertices, Loads* loads, Materials* materials,Parameters* parameters){
+
+	/*output: */
+	IssmDouble J=0.;
+	IssmDouble J_sum;
+
+	/*Compute Misfit: */
+	for(int i=0;i<elements->Size();i++){
+		Element* element=xDynamicCast<Element*>(elements->GetObjectByOffset(i));
+		J+=RheologyBAbsGradient(element);
+	}
+
+	/*Sum all J from all cpus of the cluster:*/
+	ISSM_MPI_Reduce (&J,&J_sum,1,ISSM_MPI_DOUBLE,ISSM_MPI_SUM,0,IssmComm::GetComm() );
+	ISSM_MPI_Bcast(&J_sum,1,ISSM_MPI_DOUBLE,0,IssmComm::GetComm());
+	J=J_sum;
+
+	/*Assign output pointers: */
+	*pJ=J;
+}
+
+IssmDouble RheologyBAbsGradient(Element* element){
+
+	int         domaintype,numcomponents;
+	IssmDouble  Jelem=0.;
+	IssmDouble  misfit,Jdet;
+	IssmDouble  dp[3],weight;
+	IssmDouble* xyz_list      = NULL;
+
+	/*If on water, return 0: */
+	if(!element->IsIceInElement()) return 0.;
+
+	/*Get problem dimension*/
+	element->FindParam(&domaintype,DomainTypeEnum);
+	switch(domaintype){
+		case Domain2DverticalEnum:   numcomponents   = 1; break;
+		case Domain3DEnum:           numcomponents   = 2; break;
+		case Domain2DhorizontalEnum: numcomponents   = 2; break;
+		default: _error_("not supported yet");
+	}
+
+	/* Get node coordinates*/
+	element->GetVerticesCoordinates(&xyz_list);
+
+	/*Retrieve all inputs we will be needing: */
+	Input* weights_input=element->GetInput(InversionCostFunctionsCoefficientsEnum); _assert_(weights_input);
+	Input* rheologyb_input=element->GetInput(MaterialsRheologyBEnum);                  _assert_(rheologyb_input);
+
+	/* Start  looping on the number of gaussian points: */
+	Gauss* gauss=element->NewGauss(2);
+	for(int ig=gauss->begin();ig<gauss->end();ig++){
+
+		gauss->GaussPoint(ig);
+
+		/* Get Jacobian determinant: */
+		element->JacobianDeterminant(&Jdet,xyz_list,gauss);
+
+		/*Get all parameters at gaussian point*/
+		weights_input->GetInputValue(&weight,gauss,RheologyBAbsGradientEnum);
+		rheologyb_input->GetInputDerivativeValue(&dp[0],xyz_list,gauss);
+
+		/*Tikhonov regularization: J = 1/2 ((dp/dx)^2 + (dp/dy)^2) */ 
+		Jelem+=weight*1/2*(dp[0]*dp[0] + dp[1]*dp[1])*Jdet*gauss->weight;
+	}
+
+	/*clean up and Return: */
+	xDelete<IssmDouble>(xyz_list);
+	delete gauss;
+	return Jelem;
+}
Index: /issm/trunk-jpl/src/c/modules/RheologyBAbsGradientx/RheologyBAbsGradientx.h
===================================================================
--- /issm/trunk-jpl/src/c/modules/RheologyBAbsGradientx/RheologyBAbsGradientx.h	(revision 18825)
+++ /issm/trunk-jpl/src/c/modules/RheologyBAbsGradientx/RheologyBAbsGradientx.h	(revision 18825)
@@ -0,0 +1,14 @@
+/*!\file:  RheologyBAbsGradientx.h
+ * \brief header file for inverse methods misfit computation
+ */ 
+
+#ifndef _RHEOLOGYBGRADIENTX_H
+#define _RHEOLOGYBGRADIENTX_H
+
+#include "../../classes/classes.h"
+
+/* local prototypes: */
+void RheologyBAbsGradientx( IssmDouble* pJ, Elements* elements,Nodes* nodes, Vertices* vertices, Loads* loads, Materials* materials, Parameters* parameters);
+IssmDouble RheologyBAbsGradient(Element* element);
+
+#endif
Index: /issm/trunk-jpl/src/c/modules/modules.h
===================================================================
--- /issm/trunk-jpl/src/c/modules/modules.h	(revision 18824)
+++ /issm/trunk-jpl/src/c/modules/modules.h	(revision 18825)
@@ -76,4 +76,5 @@
 #include "./ResetFSBasalBoundaryConditionx/ResetFSBasalBoundaryConditionx.h"
 #include "./RheologyBbarAbsGradientx/RheologyBbarAbsGradientx.h"
+#include "./RheologyBAbsGradientx/RheologyBAbsGradientx.h"
 #include "./Scotchx/Scotchx.h"
 #include "./Shp2Kmlx/Shp2Kmlx.h"