Graphical Path Method™
The Graphical Path Method (GPM®) is an alternative to CPM that promotes rapid, collaborative, and informed project planning. GPM allows schedules to be created more intuitively and introduces innovative concepts that improve schedule optimization and analysis.
What makes GPM unique?
Real-time calculations
When an activity is moved within a network, its relational logic is subject to breaking down. GPM heals these relationships by propagating the change throughout the network in real-time. This automatic correction is known as ‘self-healing’ and the result is dynamic preservation of logic. Since GPM doesn’t rely on a database-driven scheduling engine – dates, durations, float attributes, the critical path, and resource profiles all continuously refresh as the network is modified. These real-time calculations provide invaluable information as schedules are built.
Planned-dates
GPM omits the early start bias inherent with CPM, permitting activities to be placed anywhere within their total float range, without constraining float. This is achieved with the introduction of Drift: the number of time units an activity can gain before advancing the start of the project. In a GPM network, Drift plus GPM Float is equivalent to CPM total float. With the ability to draw and stretch activities in either direction, planned dates allow projects to be planned forward or backward, allowing schedules to be built more naturally and with more flexibility than CPM.
Forensic float
In CPM, the ability to calculate floats is lost when actual dates are entered. Not only does GPM retain this ability, but it’s inherent to the GPM algorithm. Once activities are actually completed, the meaning of float is interpreted as hypothetical: how much could an activity have been delayed? In GPM, this value is referred to as forensic float, and it continues to refresh even as schedule progress updates to the right of the data date. This can be particularly useful when analyzing a schedule for delays after the project has started or finished.
Scheduling method comparison
| – | Critical Path Method | Graphical Path Method™ |
|---|---|---|
| Diagramming Method | Precedence Diagramming Method | Logic Diagramming Method |
| Activity Placement | CPM Early Dates | Early, Late, or Planned Dates |
| Link Leeway Calculation | None | Gap |
| Activity Early Dates | Calculated from Forward Pass | Current Dates Less Drift |
| Activity Late Dates | Calculated from Backward Pass | Current Dates Plus Float |
| Activity Free Float | CPM Free Float | GPM® Buffer and Drift-Buffer |
| Can Activity Float Forward? | If Activity Total Float is > Zero | If Activity Float is > Zero |
| Can Activity Float Back? | No, Activity Drift Does Not Exist | If Activity Drift is > Zero |
| Floating by Delaying Start | Reduces Total Float | Does Not Reduce Total Float |
| Float Governing Technique | Through Mandatory Constraints | Benchmarks as Fixed Events |
| Total Floats Left of Data Date | Cannot be Determined (Always = Zero) | Recalculated if Schedule Changes |
| Software Data Structure | Database | Objectbase |
| Scheduling Algorithm | CPM Block Scheduling Algorithm | Step-wise Algorithm |
| Software User Interface | Batch (Multiple Engines) | Interactive, Real-time |