static void node_composit_exec_invertvalue(void *data, bNode *node, bNodeStack **in, bNodeStack **out)
{
       if (in[0] > in[1]){
                 out[0]->vec[0] = in[1]->vec[0] - in[0]->vec[0];
       }else { out[0]->vec[0] = in[1]->vec[0] + in[0]->vec[0];
       }
       printf("input value = %f",in[0]->vec[0]);
       printf("output value = %f",out[0]->vec[0]);

}