Resource Critical path

Dear list,



In my experience (for most schedules at least), the identified Critical Chain is not a unique solution. Thus different CC software may yield distinctly different critical chains even from the same schedule.



There are some optimizations that can be done, e.g. minimize schedule length, longer duration tasks earlier/later, etc. I agree with Larry Leach when he talks about a "good enough concept". He says (Critical Chain Project Management, p153), "No proven algorithm exists for resource leveling to ensure an optimum schedule".



In some cases, the resource leveling implementation in MS Project cannot create a resource-leveled schedule suitable for the creation of a critical chain schedule. I’m not sure when MS will have this fixed.



Cheers and have a peaceful / safe new year.



A. Faisal Shaazi, PMP

Principal Consultant

Unified Vision - Makers of Critical Chain Software



Mobile:+6012.6080.745

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OK. MS Project Example:

2 resources A and B

Activity 1, Duration 20 days, Resource A

Activity 2, Duration 20 days, Resource B

Activity 3, Duration 1 day, Resource A

Activity 4, Duration 20 days, Resource B

Activity 5 - Finish Milestone

Links: 1 preceeds 2, 3 precceds 4, 2 and 4 preceed 5.



Enjoy!

And pay attention to Total Slacks. They are not feasible, they are wrong. If resources are limited Total Slack field shall be ignored.

Vladimir,

I don’t remember this field name in english; the french name is "Jalon de fin", the field is used to simulate a milestone successor to any task that has no successor in PS8.

Look at it like the One / Multi Critical Path in MSP.

OK to look at your MSP example

Alexandre

Alexandre,

I did not find Finish milestone field in the Project List (in PS8). Though it does not matter. A schedule should not depend on turning this option to Yes or No. I think that you agree with me. The problem is worse when the schedule is large - it is hard to discover a problem.

I don’t understand why in CC mode project schedule does not change when I change activity durations (make it 10 times less and you will see huge vast periods between task execution periods).

Do you want an example for MS Project?

Hi Vlad,

I tried your test project with MSP2002 and PS8; results after resource leveling are as follows:

MSP with unique critical path: task 3 is postponed at the end of task 1

MSP with multiple critical path: cannor resolve resource leveling

PS8 with Finish Milestone set to "No": Task 2 is postponed after Task 1, project is 20 days longer than necessary

PS8 with Finish Milestone set to "Yes": task 3 is postponed at the end of task 1

To set Finish Milestone, go to Projects Table, display field and change it to No or Yes

All the best

Project Test consists of three activities (1, 2 and 3) and uses two resource units (a and b) available 8 hours per day. Activity 1 has 20 days duration and uses resource a, activity 2 has the same duration 20 days and uses resource b, activity 3 lasts 19 days and uses resource a.
Activity 1 preceds activity 2 (FS). That’s all.
Use this example in the Critical Path mode.
When I tried Critical Chain mode in PS8 a schedule did not follow changes in activity durations, all activities became ALAP and so on. It worked quite strange. I remember that PSNext does not include Critical Chain. Am I right?
Please inform me about the results of your testing.
Best Regards,
Vladimir

Hi Vlad,

sure, I’d like some straight and simple example; as I am going thru’ PSNext these days, I’ll try your example in PS8 and PSNext

Thanks

Yes, I did. The problem is in resource leveling algorithms. The software produces poor resource-constrained schedules and thus wrong critical chain.
Do you want some example?

Hi Vald,

Have you ever tried the Critical Chain capabilities?

Regards

Alexandre,

do you know that leveling algorithms that are used in Sciforma (and Scitor) produce funny results? I like your product except its resource constrained scheduling capabilities.

Hello,

have a try to Project Scheduler 8, http://www.sciforma.com

alexandre

OK, let’s hope that some day Microsoft will be able to calculate Resource Critical Path. Do you have time to wait for this some day?

I am afraid that you have no other solution except exporting your project to Spider Project software and rescheduling it there. Other packages do not calculate resource constrained floats and thus will not show which activities are really critical.