Optimization for Computational graph

[peter0627ustc]

After I visualized the computational graph through the compile_dot function, by inspecting the simplest graph (1,0,0) for GV and parquet algorithm, I found some optimizations don't work. As the graph show below:
For the parquet graph:

It's obvious to see that there are still trivial unary chains,
The same situation happen for the GV graph

The reason may be that the factor of some nodes is not 1.