Why does Prerequisite Path list tasks that run at the same time?

Topological order puts each prerequisite before the task that needs it. It does not tell you to perform every listed task one after another. Prerequisite Path calculates start times from checked dependencies, so independent tasks can overlap even when their IDs appear consecutively in that list. Read ES and EF or the printed timeline intervals to see the modeled timing.

Open Prerequisite Path

Treat the order as a dependency check

The Topological order line answers a narrow question: in what order can the app process tasks so that every prerequisite has already been processed? An ID appearing first does not reserve all the time before the next ID. Consecutive IDs in that line do not create a dependency between those tasks.

Use the line to check that a prerequisite appears before its dependent. Use the timing table and Earliest-start timeline to answer when work can begin. Those outputs describe different aspects of the same worksheet, so a sequential list and overlapping bars can both be correct.

Enter three tasks with just one dependency

For a fresh worksheet, enter A as Arrange chairs for 30 minutes, add B as Print signs for 10 minutes, and add C as Put up signs for 5 minutes. Leave A and B without prerequisites. Under Prerequisites for C, check only B. This says that signs must be printed before they can be put up; arranging chairs is independent.

Choose Analyze. The topological order is A, B, C. However, A occupies minutes 0 to 30 and B occupies 0 to 10. C then occupies 10 to 15. The project lower bound is 30 minutes, rather than the 45 minutes obtained by doing every listed task in sequence. The list has not instructed B to wait for A.

Follow the calculation behind the overlap

For each task, the app sets earliest start to the largest earliest finish among its prerequisites, or zero when there are none. It adds the task duration to get earliest finish. That is why C starts at minute 10 in this example: its only prerequisite is B, which finishes then. A does not enter that calculation.

The app constructs the topological list by repeatedly selecting the earliest entered task whose prerequisites have all been processed. With A and B both available initially, A wins that tie because it was entered first. This is a repeatable calculation order, not a recommendation to give chairs priority over printing.

Check a prerequisite entered later

Now suppose the chair arrangement really must wait until the signs are up. Under Prerequisites for A, check C and choose Analyze again. You can refer to a later-entered task; the calculation does not assume alphabetical IDs are the dependency sequence.

The order becomes B, C, A. B runs from 0 to 10, C from 10 to 15, and A from 15 to 45. The table still presents tasks in their worksheet order, A, B, C, while their offsets show the new sequence. Read the IDs and times together instead of treating table row position as start order.

Use real dependencies when deciding what can overlap

If one volunteer must arrange chairs and print signs, the first worksheet does not resolve that conflict. Prerequisite Path assumes unlimited parallel capacity and fixed durations. It has no staffing assignment. Add a prerequisite only when it represents the finish-before-start order you intend to model; the app will not choose a workable staffing sequence for you.

Every edit clears the previous result, so Analyze after changing a link before interpreting the order or saving a report. The text report records Topological order separately from the task offsets. Keep both when explaining the plan: the order establishes dependency consistency, while ES and EF describe earliest timing under the stated assumptions.

AI-assisted ForgeHub editorial. App capabilities were checked against its implementation; this guide is not an independent review.