Adding resources to fixed duration tasks

December 16, 2017 - 05:57 am
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I am struggling a bit with adding resources to a fixed duration task. Any help is appreciated.


If you have a fixed duration task, ProjectLibre does not appear to properly handle resource adjustment by work, only by units. 

...Unless I am missing something! Is this a bug?


My goal is to add resources at less than 100% (units) to a fixed duration task. This is a pretty common situation in my projects. I am assuming here that:

Work = Duration X Units

And that the behaviour should work something like the attached image (courtesy of http://epmstrategy.com/WhitePapers/EPM%20Strategy%20Task%20Types.pdf

So a hypothetical case: 5 day fixed dur, Resource A @ 50% units (i.e. 20 hrs work)

  • Step 1: add task of 5 day duration
  • Step 2: make task fixed duration and turn off effort driven
  • Step 3: assign Resource A (defaults to 100% units, 40 hrs work)
  • Step 4: adjust Resource A by:
    • Option 1: Change units to 50% --> This works as expected = total duration 5 days, work is 20 hrs
    • Option 2: Change work to 20 hours --> This does not work = 40 hours work (what!?) 200% units, total duration 2.5 days); the maths works, but the task duration was most definitely not fixed.
  • Step 5: Adding a second resource at lower work follows the same pattern above, except that in Option 2 (adjusting work), the units are correctly adjusted and the task duration is fixed. Presumably, this is because the task is driven by Resource A.

Interestingly, If I pause at Step 4 Option 2, and try to fix it back by over-writing the work again to 20 hours: work changes back to 40 hours, units are 400% and duration is 1.25 days. This keeps going, theoretically infinitely.

While the above suggests I can work around the issue by only adjusting units, this is a bit of a pain as I will need to figure out, each time, what % equates to a specific amount of work. This is even more of a pain with irrational numbers or repeating fractions. It could lead to small errors in estimates (potentially significant in the aggregate).