Multiple predecessors

[mrgipponi]

Good morning,

I'm trying to understand how to address this matter. I have 3 activities, A,B and C.
A is propedeutical to both B and C, the starting date of which are imposed.
How can I automatically have A started in date minimum (B start ; C start) - duration of A ?
It seems that the system always schedule A to maximum (B start ; C start) - duration of A

thank you

[JulieS]

I'm not sure I fully understand your question. If A is a successor to both task B and C, it will obey the later of the two. There is no method in Project to automatically select the shorter of two predecessors.

[mrgipponi]

Hi Julies,

quite the opposite. A is a predecessor to both B and C.
B and C must start at a certain date, let's say DateB and DateC.
But in order to start B and C, A must be completed, the duration of A is, let's say, 20 days.
So, when A must start ?
DateB-20 or DateC-20 ?
The obvious answer is DateB-20 if DateB<DateC.
But how can make project give the correct timing to A ?

[JulieS]

Set up a F to S relationship between both task A and B and Task A and C.

Set Must Start on Constraints to B and C. Change the constraint on Task A to As Late As Possible to calculate when A must start.

The issue with this scenario is you need to know with certainty that Task A only takes 20 days.

Personally I would leave Task A with an ASAP constraint to build in some buffer against inaccurate estimates or employee illness or vacation.