Float, Negative Float, Hard Constraints and Impact on Critical Path
Using Negative Float to See End Date Variance
In order to see end date variance, some schedulers set constraints and look at negative float to see end date variance. Negative float occurs when an activity's delay threatens to extend beyond its constraint date, potentially delaying overall project completion.
Float, Negative Float, Hard Constraints and Impact on Critical Path
SmartPM doesn't incorporate negative float because it prioritizes the true critical path, ensuring accurate project timeline identification. By disregarding soft constraints in float calculation and maintaining a zero float value, SmartPM provides clarity and enables informed decision-making. This approach mitigates risks associated with widespread negative float, avoiding confusion and facilitating better project management. Additionally, SmartPM translates negative float into "days late" for clear reporting, aligning with its focus on precise communication and decision support. This simplifies communication regarding end date variance, aligning with the original intention behind the concept of negative float.
Hard Constraints Lead to Inaccurate Critical Path
However, using hard constraints will create an inaccurate critical path. Native scheduling tools such as P6 and Microsoft Project depict multiple float paths, some of which may exhibit negative float but do not accurately represent the project's true critical path due to various constraints. For example, Primavera P6 employs the longest path critical activity definition, while Microsoft Project identifies critical activities to establish the critical path. Although the longest path may coincide with the critical path, this isn't always the case. It's possible to have critical activities that aren't part of the longest path.
Soft Constraints Allow for an Accurate Critical Path
If a schedule must have a constraint, SmartPM recommends using soft constraints such as “Start no earlier than” or “Finish no later than“ instead of hard constraints like “Must finish on” or “Must Start On” or “Start On” or “Finish on.”
SmartPM will disregard soft constraints in its float calculation. In SmartPM, the lowest float value is always zero, ensuring that the true critical path is accurately identified.
This distinction becomes particularly valuable when managing projects with widespread negative float. Without clear visibility of the true critical path, project managers risk losing control over project timelines. SmartPM mitigates this risk by focusing solely on the critical path, thereby avoiding confusion and facilitating more informed decision-making.