inline void weight_dw() {
   v_dw.scale(&v_fixed_dw); 
 }
 void resetTargetDw(const AzDvect *v_tar, const AzDvect *inp_v_dw) {
   v_tar_dw.set(v_tar); 
   v_dw.set(inp_v_dw); 
   v_tar_dw.scale(&v_dw); /* component-wise multiplication */
 }
 inline void weight_tarDw() {
   v_tar_dw.scale(&v_fixed_dw); 
 }