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Duration Calculation Bug?

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    • #4878
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      I think there’s a bug in the way that Project calculates duration on fixed work task using multiple resources. I can reproduce conflicting behavior for duration calculation on Fixed Work tasks as follows (I’ve included the ? marks that Project shows in the duration field):


      1.     Create a fixed work task and add 80 hours of work to it (duration remains at 1 day?).

      2.     Assign two resources to the task, one at 90% and one at 10% (duration changes to 10 days?). Project is splitting work between the resources in order to optimize duration.

      3.     Adjust the work to any value you want EXCEPT 0 hrs and the duration adjusts as expected (for example, duration changes to 20 days? if you change the work to 160 hrs).

      4.     Optional: directly edit the duration field to get rid of the ? mark if you want.

      5.     Now, change the work value to 0 hrs (duration changes to 0 days).

      6.     Change work back to 80 hrs (duration changes to 50 days). In this case Project is now assuming that the scheduler wants to split work evenly between the resources instead of optimizing duration (REALLY bad assumption).


      Something about changing the task to 0 hrs work and then changing work back to a positive value changes the way Project calculates the duration.  I asked this question on the Microsoft forums and two moderators replied with “That’s what you should expect” but I’m calling BS. I don’t recall this behavior from previous versions of Project. Thoughts?

      Scott Castelli

    • #6124
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      I have Project 2007 and on step two if you apply the resource at the same time you will get a different result than if you apply them one after the other.  Project keeps track of the order the resource is applied when making its calculations.
      When you set the value to 0 hrs of work, then make the change back to 80hrs, the resources are already applied to the task, so Microsoft Project splits the work evenly between both resources.
      Hope this helps….
      John Riopel
    • #6127
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      I’ve also seen some strange behavior in Project 2010 on a fixed work Task.

      I create a Task and define (in this order) Work of 12 hours and Duration of four days  I then add two Resources without specifying a percentage.  They get added at 38% each, and the Duration (as expected) gets cut in half.

      I correct the Duration, and when I tab out if the column I get the little green triangle prompt.  From the warning menu I make sure I’ve selected to change the hours the resources will work.

      This should trigger a recalculation of the Resource allocations, but that doesn’t happen.  The Work and Duration values are correct, (12h and 4d) but the Resources each still show a 38% allocation.

      I have to artificially bump the Work value up and down to trigger recalculations of the Resource allocation percents to get the correct 19%  for each Resource.

      Since we’re implementing Project Server and expect it to provide accurate Resource allocation information, the above failure to update an allocation is troubling.

      – Tom

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