Graph for Critical Path Method for task dependency management

Is this already thought?
I was working on creating a weighted directed graph implementation for adding the tasks.
Will it be necessary for calculating the weight factor of a project having a set of tasks?
If not then how will it be implemented?
Or boost's graph implementation will be used?
https://gist.github.com/Compro-Prasad/dd3d3a31f3fb1b8de6adc0283ce7f694