compute gradient analytically and not be fd approximation

[[Imported from SVN: r1711]]

src/rodsolver.cc

@@ -230,8 +230,7 @@ void RodSolver<GridType>::solve()
 
         if (this->verbosity_ == FULL)
             std::cout << "Rod energy: " <<rodAssembler_->computeEnergy(x_) << std::endl;
-        //rodAssembler_->assembleGradient(x_, rhs);
-        rodAssembler_->assembleGradientFD(x_, rhs);
+        rodAssembler_->assembleGradient(x_, rhs);
         //rodAssembler_->assembleMatrix(x_, *hessianMatrix_);
         rodAssembler_->assembleMatrixFD(x_, *hessianMatrix_);