CPM in schedules
Schedules use the standard critical path method (CPM) algorithm to assign schedule dates to each work record. Critical path method logic adjusts scheduling dates by factoring in precedence relationships, calendar information, specified start dates, and other factors.
When precedence constraints exist between work orders or tasks, you want the schedule dates to honor those relationships. Critical path method logic schedules the work to ensure that work is performed in the correct order. Critical path method logic follows certain rules to set optimal schedule dates for the work records in a schedule. The logic is based on durations, precedence constraints, and working time, and not on resource availability.
You can apply critical path method logic in the Scheduler application. Click the critical path method toolbar buttons in the graphical view.
How critical path methodology adjusts schedule dates
All work that has no dependencies is scheduled to start on the earliest scheduled start date. If the Preserved Scheduled Start Dates checkbox is selected for a schedule, the logic does not change the start date of tasks that are not dependent on others. However, independent tasks that are interruptible are moved to the earliest working time.
Interruptible work is scheduled only during work hours, as defined by the calendar in the schedule. Uninterruptible work is scheduled at the first available time. If no calendar information is associated with the schedule, all work is treated as interruptible.
Critical path method logic evaluates precedence relationships. For example, in a Finish-to-start relationship between Task 1 and Task 2, the start date for Task 2 is moved to the end date of Task 1.
Lead and lag time are added to the schedule dates as needed. For example, in the Finish-to-start relationship in the previous example, if Task 2 has a lead time of three hours, Task 2 is scheduled three hours after Task 1 finishes.
When the critical path method logic adjusts the work dates, a Start-to-finish relationship can move work to a date that is earlier than the current date. To avoid the conflict, enter a value in the Start Date field on the schedule. The logic does not schedule any work earlier than the specified start date. This date is also used in cases when the work records have no target or schedule dates.
When CPM is run on a schedule, the critical path is highlighted. The critical path indicates the records that have no float, meaning if their dates slip, the entire project slips. You can configure the color of the highlighting (skd.criticalpath.color) and enable warning messages (skd.cp.impactwarning.enabled) for CPM in the System Properties application.
Critical path method logic does not affect preventive maintenance forecasts in the schedule.
Identifying the critical path
After running CPM, the critical path is highlighted in the graphical view. A backward pass
calculates the late dates and float to determine the critical path, allowing users to focus on the
important tasks that drive the schedule finish date. You can filter to show only the critical path
by clicking Filter by Critical Path 
.