A brief history of Scheduling

Thank you, Mimoune,
I will look at this development.
I don’t expect that genetic algorithms will be efficient for large projects but in any case it is interesting.
Best Regards,
Vladimir

Hi Vladimir,

Do you have any idea about what these guys are using:

http://www.quintiq.com/
"
Advanced Planning & Scheduling Software Solutions
Quintiq Advanced Planning & Scheduling software is unique in the sense that it comprises standard software creating an exact fit to the customer’s needs. The Quintiq advanced software is applicable for strategic, tactical and operational planning and real time event management needs. Unique are the large scale and multistage planning solutions that can be created with Quintiq, enabling it to provide integrated enterprise wide, multi-site and (logistic) supply chain solutions.

Advanced Planning & Scheduling Software Solutions that empower your competitive advantage by enabling you to solve the most complex planning and scheduling puzzles.
Employee Scheduling (Staff, Employees, Shifts and Personnel)
"

With kind regards,

Samer

samer

as i am on my rotation, i got some time to read about mathematics ;) from my understanding CPM algorithm is a very simple mathematic problems and there is no reasonable reason to have different output by different software. because there is only one solution to the problem (i suppose we use some calenders, resource are unlimited)

but once we start speaking about resource constraints, it become different stories as it become NP-hard problem.

http://en.wikipedia.org/wiki/NP-hard

so actually each software use different heuristic algorithm, and different approach, thus different results.

it will be interesting to have a independent study to compare the robustness of each software package regarding scheduling under limited resources.

best regards

Samer,

In general terms the tools can be called to be part of applied mathematics.

Look for the following applied mathematics terms; Operations Research and Applied System Analysis. Also look for the terms; algorithm, branch and bound, linear programming, non-linear programming, queuing, mathematical simulation and Monte Carlo Simulation.

Best Regards,
Rafael

Hi Samer,
I never heard about Quintiq.
I will look at their site.
Mimoune described the problem correstly:
CPM is very easy and different softwares will produce different results only when they uae different constraints (ALAP in P^ and Spider is not the same as ALAP in MS Project).

Spider Project includes resource constrained scheduling optimization algorithms that produce the solution that is close to optimal.
Besides it levels materials and costs.
This is much more complicated.

Regards,
Vladimir

Dear Rafael,

I have completed all the courses graduate and undergraduate in Civil Engineering. Statics, Dynamics, Operation Research, linear and non-linear theories, and I have taken close to 1000 training hours in the past 3 years in different fields :).

Please note that I have also written a three dimensional finite element analysis program for Structural frames twenty years ago. But this is not what I did since then. I have been managing projects.

The last Internation software black box that I debugged 14 years ago took me 9 months and i found around 70 errors. Do not worry about my mathematical understanding of CPM, it is simple. But I do not have the time to get into it at the moment.

I think some common sense and an excel sheet is enough to manage up to $500M projects in my experience.

With kind regards,

Samer

Dear Mimoume and Vladimir,

Once we start talking about "NP-hard problem" or any other mathematic theories, then it is not CPM. And you can not associate it with CPM because CPM is simple.

I agree with you that current softwares in the market have their own add one. But I also believe that CPM results for the same model must not change from one software to another. When you keep it simple, you can predict it. If you try to use the fancy options that the "user friendly" softwares is offering, and you have no idea about the mathematical formula that is governing the equations when you press the botton, then how would you be able, as a user/ responsible party, to expalin then and be responsbile for them.

With kind regards,

Samer

Samer that’s exactly what i have said before CPM is a simple method, and btw i don’t understand why ALAP is different from spider to ms project !

but CPM don’t take into account resource constraints, now different software have different output. and each package has a different approach

http://pmbook.ce.cmu.edu/10_Fundamental_Scheduling_Procedures.html#10.9 Scheduling with Resource Constraints and Precedences.

Samer , just to make it clear i am not pretending to have a clue about all this, i am just learning.

best regards

mimoune

Hi Mimoune,

What I find amazing is that we continue to use the same thing without improving it. This is a unique natural thing it seems. Using the process for 50 years without improving it.

We know that 1+1=2 and we know that CPM is logical because you get to understand the small example. But once you get to multiplications on the order of thousands of activities, your calculator is the black box, and your refined management system to make sure that you input the data correctly.

I think that we have 50 years old engine on nice sport car now. All it take is a team of 10 people at MIT or at Vladimir’s company for a year or two and we will have a new engine.

With kind regards,

Samer

Hi,

This is the recent evolution in CPM per google:

Using Relationship Diagrams to Enhance the Critical Path Method

www.oracle.com/ocom/groups/public/@ocom/documents/.../042744.pdf

With kind regards,

Samer

Samer,

The following is the full link as copy and paste of the posted did not work.

http://www.oracle.com/ocom/groups/public/@ocom/documents/webcontent/042744.pdf

For a start I find it to be a paper directed to satisfy the ego of the author "compliant with RDCPM". The use of codes to identify relationships in CPM started with the development of the very first network, even activities do have codes or names, and there is nothing new.

It confirms my suspicion that Mr. Plotnick is biased towards Primavera Oracle as well as many other members of the PMI. It is not that the paper is wrong, is the way the issue is presented. Instead of filling his ego by certifying compliance with a specific procedure he should be working with Primavera to provide true Float values after resource leveling.

I believe Primavera Risk does not creates the resource links for you, you still got to manually enter them, it does not even calculates true float unless you figure it out yourself these relationships that can change whenever you update the network.

Can Primavera Risk provide you with the resource dependencies relationships and true float after resource leveling a 2 activities job, none linked to the other by predecessor/successor logic, both requiring the same resource of which only one is available? If the answer is no then what is the value of the certification?

Best regards,
Rafael

PS. Done, article to the garbage can.

Dear Rafael,

Here is an article with a sensible conclusion:

A Critical Look At Critical Path Analysis
I’ve finished so I’ll start
A critical look at critical Path Analysis

John Bolton, Programmes Director, Parallel Project Training

http://blog.parallelprojecttraining.com/project-management-a...

Thanks to google of course.

With kind regards,

Samer

Hi PP,

This sounds interesting:
"
Title: Integrated models for construction planning: object flow and relationship
Author(s): M. ALSHAWI, Z. HASSAN

Journal: Engineering, Construction and Architectural Management

Year: 1999
Volume: 6
Issue: 2
Page: 197 - 212
ISSN: 0969-9988
DOI: 10.1108/eb021112
Publisher: MCB UP Ltd

Abstract: Sharing and exchanging information between project participants are basic requirements for developing construction plans. An isolated construction planning knowledge-based system is no more useful and beneficial than any another ‘island of automation’ unless the integration with other construction applications are addressed. This paper proposes conceptual data and process models for a construction planning system, CONPLAN (Intelligent CONstruction PLANning), which works within a fully Integrated Construction Environment (ICE). An object oriented methodology (James Martin) has been used to establish generic construction models within which other construction applications can be integrated. This paper also introduces briefly the modularized approach that has been adopted to integrate the various construction applications over the project life cycle.
"

With kind regards,

Samer

Hi PP,

This is common sense talking:

When is the Critical Path Not the Most Critical Path?

http://www.icoste.org/AACE2008 Papers/Toronto_ps07.pdf

I am sure that something good will come up, but it is taking time.

With kind regards,

Samer

Hi PP,

This paper has a good title, and info, but not a clear conclusion. I am sure that some elements will be used in the new solution:

The time-cost trade-off analysis in construction project. www.tede.vgtu.lt/upload/ukis.../tede_vol15_no4_523-539_blaszczyk.pdf

If you do not get the link, cut and paste the title in google.

With kind regards,

Samer

I am a big fan of google.

"Research on the fully fuzzy time-cost trade-off based on genetic algorithms "

Jin Chao-guang1, 2, Ji Zhuo-shang1, Lin Yan2, Zhao Yuan-min2 and Huang Zhen-dong2

(1) Ship CAD Engineering Center, Dalian University of Technology, 116025 Dalian, China
(2) Dalian Shipyard Co. Ltd., 116005 Dalian, China

Received: 21 June 2005

Abstract It is very difficult, to estimate exact values of time and cost of an activity in project scheduling process because many uncertain factors, such was weather, productivity level, human factors etc., dynamically, affect them during project implementation process. A GAs-based fully fuzzy optimal time-cost trade-off model is presented based on fuzzy sets and genetic algorithms (GAs). In tihs model all parameters and variables are characteristics by fuzzy numbers. And then GAs is adopted to search for the optimal solution to this model. The method solves the time-cost trade-off problems under an uncertain environment and is proved practicable through a giving example in ship building scheduling.
"

If anyone gets the complete paper, please offer to share what the details are.

With kind regards,

Samer

Hi,

This might offer another solution as well:

"
Productivity Scheduling Method: Linear Schedule Analysis with Singularity Functions

Gunnar Lucko,1 A.M.ASCE
1Assistant Professor, Dept. of Civil Engineering, Catholic Univ. of America, Washington, D.C.

This paper describes a new integrated method of linear schedule analysis using singularity functions. These functions have previously been used for structural analysis and are newly applied to scheduling. Linear schedules combine information on time and amount of work for each activity. A general model is presented with which activities and their buffers can be mathematically described in detail. The algorithm of the new method forms the body of the paper, including the steps of setting up initial equations, calculating pairwise differences between them, differentiating these to obtain the location of any minima, and deriving the final equations. The algorithm consolidates the linear schedule under consideration of all constraints and, thus, automatically generates the minimum overall project duration. The model distinguishes time and amount buffers, which bears implications for the definition and derivation of the critical path. Future research work will address float and resource analysis using the new model.

"

But all these solutions need funding to come up with some commercial new tool.

Time for the tool makers to invest in the future.

With kind regards,

Samer

Hi PP,

The is another natural solution:

Applying an Ant Colony Optimization Algorithm-Based Multiobjective Approach for Time – Cost Trade-Off
by Ying Xiong, Ph.D. Candidate, (School of Economics and Mgmt., Beijing Jiaotong Univ., Beijing 100044, China. E-mail: xy72@yeah.net) and Yaping Kuang, (Instructor, School of Civ. Engrg. and Arch., Zhejiang Univ., Hangzhou 310027, China; and, Ph.D. Candidate, School of Economics and Mgmt., Tongji Univ., Shanghai 200092, China.

Journal of Construction Engineering and Management, Vol. 134, No. 2, February 2008, pp. 153-156,

Abstract: The time.cost trade-off is one of the most crucial aspects of construction project planning, which in fact is a combinatorial optimization problem. This technical note employed an evolutionary algorithm — ant colony optimization (ACO) algorithm to deal with the time – cost trade-off problems. Combining with the modified adaptive weight approach, the ACO algorithm can find out the optimal solutions, and define the Pareto front as well. The development of the ACO-based multiobjective approach in this technical note provides an attractive alternative to solving construction time – cost optimization.
"

So with the help of google, I think that the tool makers can find plenty of improved solution on the net.

With kind regards,

Samer

Dear Rafael,

Now the Dynamics factor comes in. Not at the right time of Scheduling, but this is a start. With the help of google:

"
FLORA: New Forensic Schedule Analysis Technique
by Long D. Nguyen, Ph.D., (Constr. Consultant, Jax Kneppers Assoc., Inc., Walnut Creek, CA 94598. E-mail: long@jaxkneppers.com) and William Ibbs, (Prof. of Constr. Mgmt., Dept. of Civ. and Envir. Engrg., Univ. of California, Berkeley, CA 94720; presently, Pres., The Ibbs Consulting Group, Inc., 5932 Contra Costa Rd., Oakland, CA 94618 (corresponding author). E-mail: drcwibbs@aol.com)

Journal of Construction Engineering and Management, Vol. 134, No. 7, July 2008, pp. 483-491, (doi 10.1061/(ASCE)0733-9364(2008)134:7(483))

-----------------------------------------------------------
Document type: Journal Paper
Abstract: While various factors such as float ownership, logic change, and resource allocation (FLORA) affect results of delay analysis, existing delay analysis techniques tend to ignore most if not all of them. To address this insufficiency this paper proposes a new schedule analysis technique called FLORA that simultaneously captures the dynamics of float, logic, and resource allocation in its analyses. FLORA analyzes not only the direct impact of a delay but also its “secondary” effect. The analysis process follows ten rules that are flexible and customizable. A case study is employed to illustrate its application. FLORA yields different and more reasonable outcomes compared to the window analysis technique. Each single analysis may also yield different or even conflicting results. By properly dealing with the current issues of schedule analysis, FLORA can be more reliable. Practitioners may readily accept its analyses and outcomes because they are able to specify, modify, and consent to the rules for schedule analysis to fit into a specific context in advance. Researchers may further evaluate the impacts of different factors on delay responsibility or apply FLORA to real projects to assess its strengths, weaknesses, and potential improvements.
"

If anyone gets the paper, please share what they are talking about in more details. It would be interesting to know.

With kind regards,

Samer

Samer,

Thanks for the reference, is not available because it is a for profit article. Found the PhD Thesis available on the web. I will take a look at it latter as we just got awarded a new job. I also found on the web a presentation in Chinese or Vietnamese but the few English words got me interested.

Best regards,
Rafael

Dear Rafael,

Let me read what you come across. It will be interesting.

Make sure that you read the artical in post 115.

With kind regards,

Samer