IDing the Critical Chain

[Cristina Pupper]

Hi-

I am looking for a macro that will identify the path(s) through a resource
leveled project that have no "slack". I know Project is based on CPM, but
the critical path is not of much use once you level resources.

Thanks!

Cris

 

[Dale Howard [MVP]]

Christina --

Click the Gantt Chart Wizard button and set it to display the Critical Path
for you. Any task which has a Total Slack = 0 days will be formatted with
red Gantt bars. Hope this helps.

 

[JackD]

I don't know exactly how this would work.
The longest resource leveled path is presumably the "critical" path, but the
dependencies between the tasks are not explicit. I suppose it is possible to
artificially insert resource dependencies which would tie together a
specific resources tasks (in serial order) and then use them to calculate
the critical path. This could be done programmatically with VBA, and then
something like my trace dependencies macro could be run on it to identify
the critical path, but I'm not sure what more it would tell you.

What are you thinking you would learn from this?
How would you expect it to work?

-Jack

 

[Trevor Rabey]

It is often useful to be able see the unlevelled CP and the levelled CP.
If you use View>Toolbars>customise you can add the LEVEL NOW and CLEAR
LEVELLING buttons to your menu bar.
Turn auto levelling off. Then level and unlevel and compare the two
situations. You can save a levelled version and an unlevelled version of
your plan.
They are both useful.

 

[Cristina Pupper]

I'll use a simple example to illustrate what I am trying to do:

Given a 5 task project. R1 and R2 each have 100% available units.

1) Start Duration = 0d
2) T1 Duration = 1d, Pred = Start, Resource = R1 (100%)
3) T2 Duration = 1d, Pred = Start, Resource = R1 (100%)
4) T3 Duration = 1d, Pred = Start, Resource = R2 (100%)
5) End Duration = 0d, Pred = T1, T2, T3

Without resource leveling, all tasks are critical (no slack).

When you level the resources (assume T1 has higher priority than T2), T1 &
T3 start on Day 1, T2 starts on Day 2. T2 is now the only task that is
critical, T1 & T3 each have 1 day of slack. BUT, if T1 slips, because of
resource constraints, T2 will slip. So T1 acts like it has no slack.

A PM that just followed the CPM used by project would think T1 could be
delayed by 1 day and not affect the project when in actuality, a delay in T1
will delay the project end date. I want to know which tasks that if delayed,
will cause the project to be delayed. To get this info, you could go in and
put hard links to represent the resource constraints (i.e. make T1 a pred of
T2), but that is a lot of extra work for a decent size project

Cris

 

[JackD]

I'll use a simple example to illustrate what I am trying to do:

Given a 5 task project. R1 and R2 each have 100% available units.

1) Start Duration = 0d
2) T1 Duration = 1d, Pred = Start, Resource = R1 (100%)
3) T2 Duration = 1d, Pred = Start, Resource = R1 (100%)
4) T3 Duration = 1d, Pred = Start, Resource = R2 (100%)
5) End Duration = 0d, Pred = T1, T2, T3

Without resource leveling, all tasks are critical (no slack).

When you level the resources (assume T1 has higher priority than T2), T1 &
T3 start on Day 1, T2 starts on Day 2. T2 is now the only task that is
critical, T1 & T3 each have 1 day of slack. BUT, if T1 slips, because of
resource constraints, T2 will slip. So T1 acts like it has no slack.

A PM that just followed the CPM used by project would think T1 could be
delayed by 1 day and not affect the project when in actuality, a delay in T1
will delay the project end date. I want to know which tasks that if delayed,
will cause the project to be delayed. To get this info, you could go in and
put hard links to represent the resource constraints (i.e. make T1 a pred of
T2), but that is a lot of extra work for a decent size project

Cris

That is why I suggested some VBA to do it for you. Conceivably you could add
those dependencies automatically (and if you are smart you would have some
way to remove them automatically as well). I don't have a macro which can do
it but I think that the following is what I would do.

Go through the project resource by resource
For each resource determine the assignments
For each assignment find out if any of the other assignments are immediately
preceding it.
If there are then link the two activities that the resource is assigned to.

-Jack