Skip to main content

Academics using AIMMS

A dedicated space for academics and researchers to connect, ask questions, share research insights, and explore academic opportunities with AIMMS.

207 Topics
mohansx
mohansxFormer AIMMSian
published in Academic News & Opportunities
Team NP Die Hard from University of Edinburgh wins the 12th AIMMS-MOPTA Optimization Modeling CompetitionNews

The results of the 12th Annual AIMMS-MOPTA Optimization Modeling Competition are in! The competition took place virtually this year. We are very happy to share that all three of this year’s finalists solved the problem quite differently and went beyond what we expected, each solution very valid on its own. Congratulations are in order for Team NP Die Hard from University of Edinburgh, who won the competition this year.About this year’s Problem StatementWhen we were designing the problem statement with Dr. Boris Defourny, Assistant Professor at Lehigh University, we wanted to explore how mathematical optimization and machine learning approaches can work in tandem. Like always, the problem also had to be open-ended.  It needed to have multiple correct solutions rather than one absolute solution. So, we settled on a Capacitated Vehicle Routing Problem with Time Windows (CVRP-TW) and added complexity by adding constraints or withholding data that is typically known in such problems to mimi

9791
Gertjan
AIMMSian
Mstislav Simonenkov
AIMMS Champ
Mstislav SimonenkovAIMMS Champ
posted in Research & AIMMS Questions
Share your favorite OR Blogs

Good afternoon!I would like to invite the community to share their favorite blogs on mathematical programming, operations research, and data manipulation.My favorite blog is http://yetanothermathprogrammingconsultant.blogspot.com/The author of the blog uses GAMS. Models created in GAMS can be converted to AIMMS.https://how-to.aimms.com/Articles/312/312-convert-gams-to-aimms.html 

763
Gertjan
AIMMSian
mohansx
mohansxFormer AIMMSian
published in Academic News & Opportunities
Announcing the AIMMS-MOPTA Optimization Modeling Competition 2021News

This year marks the 13th edition of the AIMMS-MOPTA Optimization Modeling Competition. This year's MOPTA conference will be held at Lehigh University from August 2-4, 2021. The 13th Optimization Modeling Competition is now open and submissions are due by May 21st, 2021. The goal of this year's competition is to develop frameworks to solve the H-SARA (Home - Service Appointment, Routing, and Appointment Scheduling) problem. The aim is to efficiently hire and assign teams to customers requesting service appointments at home. The different decisions that need to be optimized here are:How many service teams are required on a particular day? Which customers are serviced by which team and in which order?We believe this will be a problem of huge interest with the recent lifestyle changes brought by the COVID-19 pandemic. For instance, an increasing number of professionals are working remotely from their homes, driving up the load on internet networks. Internet providers need to ensure that th

3200
mohansx
G
Guus KattenbeltEnthusiast
asked in Research & AIMMS Questions
Standardize link to latest version

Hi all,Every time we update our app, I get e-mails from users that they cannot enter the app and they send me a picture like the one below. We have tried to prevent this from happening by using the ‘latest’ tag option. All links in our information channels link to our app ending with the ‘/tag/latest’ such that they always end up at the right version of the app. But still I get a lot of these e-mails.Mostly this is because, once people have entered the app, they bookmark it (or store the url) and use this bookmark later on. The problem is that once they bookmark it, the url has changed to the current version name and therefore the link doesn’t consist of this latest tag anymore. And thereby causing the problem of the picture below after a new update of the app. I always reply back that they should use the link with the latest tag in there, but as we have a lot of users, this keeps happening. It would be great if there could be a solution, such that my users don’t have be annoyed by the

19814
Jan-Willem
AIMMSian
R
AIMMS Partner
royAIMMS Partner
asked in Research & AIMMS Questions
How to write Floor or ceiling Function?

Hi,I want to write a floor function in my model.Or how to get floor value of a fractional number?how can i write that in AIMMS?

981
deannezhang
AIMMS Champ
M
MantombiNewcomer
posted in Research & AIMMS Questions
Not getting correct results for leading times, phasing in capital and life of plant

The data for leading times, phasing in capital and life of plant was imported to the model. A new declaration called Lead times was added. It looks like this: All the identifiers in the Lead Times declaration are supposed to take care of the leading times, phasing in capital and economic life. However, that is not happening. Ideally:The new power plants are supposed to be committed any time between 2013 and 2050. No new capacity is supposed to start at 2013 because of leading times. Those power plants with life of plant that pass 2050 are supposed to remain active until their corresponding life of plant comes to an end.  Not all the capital can be taken in one year for new capacity, but a portion per each year of the leading time, according to p_phaseIn parameter.The attached model, opens on this page:One will have to:Click the input data button Select the scenario analysis, then click solve the scenario button. This solves the deterministic model. The corresponding results can be view

430
M
M
MantombiNewcomer
asked in Research & AIMMS Questions
Error when importing percentage data from Excel to an AIMMS model

I have been trying to import the phasing in capital data which is in the attached Excel file. I have added the identifiers on the attached word file. The data I am importing has numbers which I want AIMMS to convert to percentages.On my side the PhasingInCapital is a worksheet inside the Input Data workbook. Here is the error:ExcelSetActiveSheet(Input Data.xlsx, PhasingInCapital) failed: Workbook doesn't contain the specified sheet. Invalid index.I have imported a lot of data files from Excel, I am not sure what am I doing wrong this time.Please assist.

1022
mohansx
G
Gloria QuintanillaFormer AIMMSian
published in Research & AIMMS Questions
Improve Solve Times for your AIMMS Models with ODH-CPLEX

ODH-CPLEX is a high performance solver for Mixed Integer Programming (MIP) and Mixed Integer Quadratic Programming (MIQP/MIQCP) problems. ODH-CPLEX uses the CPLEX solver underneath and is made to run on modern multiprocessor machines. While it is designed for scheduling problems, it’s been deployed effectively on packing and other supply chain applications as well. We have noticed considerable runtime improvements for customers who use the CPLEX solver and ODH add-on. To give you more insight into these benefits, we invited the solver’s creators, Optimization Direct, for a webinar. Get a summary below or watch the full presentation by Dr. Robert Ashford and Dr. Alkis Vazacopoulos here. Improving Solve Times for Large Scale Optimization  As supply chains become more complex, models are becoming larger and equally complex to run. ODHeuristics offers a toolset for handling large and/or difficult MIPs. The ODH-CPLEX solver goes further than CPLEX in finding an initial solution. It improves

2030
G
Zahidah Mohd Zaulir
Zahidah Mohd ZaulirExplorer
asked in Research & AIMMS Questions
Stop in the middle of run

Hi, My model took more than 14 days to run on i7 core computer with 16GB RAM. And it still does not give an optimal solution yet. What will happen if we stop AIMMS during the middle of running a model when the solution is not optimal yet? The gap in progress window shows 38.2% for 10 days (see attached picture), then it drops to 38.1% on day-13. From what I understand, the gap is the difference between a best known solution and the best bound. If I set the gap to certain values, which part of the model will be affected? Will all the constraints be satisfied/evaluate? Or will AIMMS only satisfied half of the constraints? For your information, my objective is to maximize the preferences of the lecturer. My preferences parameter has the range values from 1 to 5, where 1 is least preferred while 5 is the most preferred.  Can anyone help me? Thank you in advance! Gap on Day-12  

5634
Zahidah Mohd Zaulir
M
MantombiNewcomer
posted in Research & AIMMS Questions
Adding leading time, phasing in capital and economic life to a generation capacity expansion planning model

Good day, I have an electricity capacity expansion planning model which was developed in AIMMS and is working fine. However, now I need to add the following:Lead times, which differ for each technology. Currently, the model assumes that if a technology is selected by the model, it can produce electricity as soon as the model makes it available for capacity allocation. I need this to change and the model should make the technology’s capacity available after the lead time has expired. Phasing in capital, which also differ for each technology. The current model assumes that the capital for a chosen technology is payable immediately. The phasing in capital are connected to lead times. For example if a technology has a lead time of 2 years, the phasing in capital is also over 2 years, say 90% of capital is payable in year 1 and 10% in year 2. I need the capital for each technology to be phased in according to the phasing in capital percentages.  Life of plant (Economic life), which also dif

780
M
S
sineplexusExplorer
asked in Research & AIMMS Questions
Determine where the robot has to drive

Hello dear AIMMS Community, currently im working on a simulation of robots driving in a parking garage and charging electric vehicles.The first step is done and it is kind of working, but i have currently two major problems. even if i am not putting any demand on the parking lot the robots drive to the lot and “simulate” charging an electric vehicle.  → i tried to find a solution in the community, but i was not successful. Is there any possibility, any constraint which could make  the robot not to service/drive to that parking lot while Demand(i)=0. As you can see in the picture: even if i put Demand of almost every parking lot=0, the robot drives to all the places, before going back to the depot.   Another problem is, that i want to make the robots drive on a specific route,  shown as yellow in the picture/simulation.  → Is there any chance of making the robots drive a minimum besides the yellow route? My thought is that, despite being able to create that, later in the mathimatical pr

1063
S
G
Gloria QuintanillaFormer AIMMSian
published in Academic News & Opportunities
This is a Great Time to Do OR: Prof. Laura Albert on The Relevance of Operations Research TodayInterview

We often get to speak with well-known Operations Research practitioners and professors who are dedicated to inspiring students and advancing the discipline. This time, we are excited to share experiences and insights from Prof. Laura Albert from University of Wisconsin-Madison. You might know Laura from her blog, Punk Rock OR, or her work on sports analytics. We interviewed her recently to get her take on how Operations Research is faring amid today’s uncertainty and what OR professionals can do to make a difference for social good.People in the OR community know you as a prolific researcher and blogger. Can you tell us briefly about yourself and how you came to work in this field? I was a bit of a latecomer to the field. During college, I took a course on optimization and figured out that I was very interested in how you can use mathematics to support interdependent decision-making. My PhD thesis focused on aviation security and for most of my career, I have been passionate about publ

6710
G
M
MiladNewcomer
posted in Research & AIMMS Questions
Simplex task solved mathematically - how to program it in AIMMS?

Hello, I am a Master Student at the University of Applied Sciences. I found your website by chance, because you have knowledge in production management. Recently we started working in production management with the software AIMMS. However, I don't know how to transfer or programming the simplex-modeling, which I solved mathematically, into AIMMS. Can you help me with this? 

862
M
A
Amritbir1Explorer
asked in Research & AIMMS Questions
solveFixed using AIMMS

Dear Community; We are working with some MILP problems where we need to identify the ShadowPrice of some constraints. These constraints are made up of both binary and continuous variables. As the duality is not well defined for MILP problems, one method to find the ShadowPrice is to run a LP fixed model right after MILP solution. I see that AIMMS provide ShadowPrice by default for MILP problem when the variable property “ShadowPrice” is defined. We need to know how AIMMS calculate ShadowPrices for MILP problem? Does AIMMS use a method similar to post MILP fixed LP execution? A quick additional question: Is it possible to identify and set all Bianry and Integer as “nonvar” (i.e. if var is Binary then var.nonvar := 1) -- the idea here is to manually prepare a fixed LP? I do not see how AIMMS support fixed LP preparation and its execution. Thank you;Amrit Gill

1722
A
H
HosseinMehdipourEnthusiast
asked in Research & AIMMS Questions
Very long execution time with BARON solver

Hello,I am solving small MINLP problem using BARON solver to find the ‘optimal’ solution. But for such a small system, 8 hours passed and I have not got the solution yet. My question is: why this solver cannot find the solution after such a long time? Is this because of the way I implemented the model? (If so, I am attaching my code here to let you know how I did it). I would appreciate it if you could help me solve this problem. Thank you!Regards

4914
H
P
PaulafernaliaNewcomer
asked in Research & AIMMS Questions
MIP Start with CPLEX

Hi, I would like to know how I can give an initial integer solution to a MIP solved with CPLEX. I found this link on the topic but I’m not convinced about the option it suggests for CPLEX in particular “Advanced basis” sounds like a setting to warm start an LP, not a MIP. I’m also not sure how to actually give my heuristic solution to CPLEX after that.https://how-to.aimms.com/Articles/108/108-kb11-mip-initial-solution.html.I also found this related question, but the link in the selected answer seems to be broken: https://community.aimms.com/developers-math-or-programming-39/how-to-start-solving-with-an-initial-solution-466.Thanks

9533
Marcel Hunting
AIMMSian
G
Gloria QuintanillaFormer AIMMSian
published in Research & AIMMS Questions
How OnLocation Analyzes the Impact of Renewables and Energy Storage on the U.S. Power GridBlog

OnLocation is an energy consulting company based in the Washington, D.C. area. They have extensive experience using integrated energy modeling to assess the costs and benefits of energy policies and technologies and provide insights into potential implementation challenges. OnLocation’s primary integrated modeling tool is The National Energy Modeling System (NEMS), which is the most trusted integrated energy model used for projections and policy analysis in the United States. Recently, we hosted a webinar to hear about OnLocation’s REStore model, a submodule of NEMS built in AIMMS. REStore represents electricity storage and the temporal pattern of renewable generation. Get the inside story below!Renewable energy on the riseAccording to the U.S. Department of Energy, solar installations in the U.S. have grown 35-fold since 2008. The average cost of solar photovoltaic (PV) panels has dropped nearly 50% since 2014, as well. This growth in renewables is posing new challenges for the electr

4990
G
D
Dick den HertogEnthusiast
posted in Research & AIMMS Questions
Next Analytics for a Better World is on October 28

1. The next Analytics for a Better World Webinar (ABW-W) is on Wednesday, October 28, 2020, EDT 12:00 PM (Boston time), CET 5:00 PM (Amsterdam time). Speaker: Jean-Philippe Vial (Geneva, Switzerland)Title: Analytics for the Design of Gravity-Driven Water Distribution Systems for Poor Rural Communities: the NeatWork Tool.Abstract: NeatWork is an optimization and simulation tool for the design of water-distribution systems with the aim of providing clean water to poor rural communities. The management of such systems must be cheap and simple, a requirement which prohibits power-driven equipment, such as pumps, and man-operated devices, such as regulators. Therefore, the physical system must be driven by gravity only. It must also be endowed with self-regulation to ensure flow invariance despite stochastic intermittent water withdrawals by independent users. The formulation as a least-cost design problem belongs to the realm of two-stage stochastic optimization, in which the second stage

860
D
T
Thijs Busger op VollenbroekNewcomer
asked in Research & AIMMS Questions
Subset creation/formulation

Hello all,I am trying to create a subset of a main set for a constraint. See the attached figure of the constraint*. The index k should be a subset of its set. The main set consists for example of three classes {1,2,3}, then its subset should consist be{1,2}, so the main (ordered) set minus the last element, as it is used in the constraint by (k+1) on the right-hand side. Can anybody help me out how to formulate this?* I am aware on the non-linearity

1751
gdiepen
AIMMS Champ
J
janainamarchesiNewcomer
asked in Research & AIMMS Questions
Memory ram manage

We have 2 aimms licenses, we would like to place them on the same server, is it possible to use one license for each project? Is it possible to manage ram memory used by the program being run by each license?

1052
Gertjan
AIMMSian
G
Gloria QuintanillaFormer AIMMSian
published in Research & AIMMS Questions
Analytics to the Rescue: Join AIMMS' N.S. Krishnan at INFORMS' Virtual Regional ConferenceNews

Join us this month at INFORMS' virtual regional conference! AIMMS' N.S. Krishnan (@nsk) will participate on the Panel Discussion "Analytics to the Rescue" on September 24, 12:25pm CST.About the conferenceThe conference will address the relevance of analytics to solve emerging issues, problems and challenges. INFORMS Chicago Chapter and INFORMS Analytics Society will bring together innovative and insightful leaders across multiple industries and education for this annual conference. The goal is to have in-depth discussions and exchanges of experience and ideas related to solutions during these tough and uncertain situations. The conference will take place virtually.Areas of focus include AI & machine learning, epidemic and healthcare analytics, and election analytics. Join us to hear from experts and exchange ideas on mission critical and timely applications, strategies, and processes.  Will you attend the conference? Are you working on an OR/Analytics project to help address some o

891
N
AIMMSian
N
nick98Explorer
asked in Research & AIMMS Questions
How to delete all elements from a set prior to each execution

Hi,as the title indicates I’d like to delete all elements from a set prior to each execution. Otherwhise elements from the previous execution are messing up my results. Basically I have a set that will only contain elements under a certain condition, but if it doesn’t it still keeps the elements from the previous execution right now. I tried to fix this by calling empty MySet in the MainExecution, MainInitialization or  PostMainInitialization procedures. This just gives me an error saying “The defined domain set “MySet” cannot be emptied”. I don’t quite understand what’s causing the issue here since the set should already be defined, especially when PostMainInitialization gets run after the initialization completed. Can anyone help me out with this?Thank you!  

1421
Gertjan
AIMMSian
Jess Es
Jess EsGrand Master
published in Research & AIMMS Questions
Suggested reading: Academic paper about Constraint Programming with AIMMS

Some of you may find this paper interesting - published 2013 but still relevant! “Developing Constraint Programming Applications with AIMMS” by Prof. Willem-Jan van Hoeve of Carnegie Mellon University Download the full paper in PDF from https://www.andrew.cmu.edu/user/vanhoeve/papers/aimms_cp_app.pdf Abstract. We describe the constraint programming interface of the optimization modeling systems AIMMS. First, we present the modeling language for basic constraint programming and advanced scheduling constructs, and specify how search can be controlled. Then we provide three example applications that illustrate how AIMMS can be used for developing constraint programming applications.  

2200
Jess Es
D
Dick den HertogEnthusiast
posted in Research & AIMMS Questions
New initiative: Webinar for Analytics Practitioners

New initiative!   Webinar for Analytics Practitioners (WAP) Back to School   For Analytics practitioners it is difficult to remain up-to-date with respect to the newest scientific developments that are relevant for practice. There are at least two reasons why this is difficult for them: There are many Analytics related scientific journals, but most of the papers are not relevant for practitioners. For practitioners it is very difficult to detect which of these papers are really relevant. This is one of the reasons why many Analytics practitioners who have an Operations Research background are not aware of the potential of, e.g., adaptive robust optimization, the modeling and solver power of conic (esp. conic quadratic and exponential cone) optimization, the optimization power for machine learning, etc. The Analytics field is multi-disciplinary with respect to its methodology. It not only consists of Operations Research methodology, but also a significant part of Statistics and A

8334
Jess Es
N
nick98Explorer
asked in Research & AIMMS Questions
How to define a set as empty under a certain condition

Hi,I think it would be helpful to provide a little bit of background regarding my problem first. I’m currently working on a project where a given set of volunteers should be assigned to a given set of people in need. So basically a simple transport problem, where the demand of all people in need is 1 and the supply of all volunteers is 1. The model in AIMMS always expects a balanced problem. So in case of a surplus on either side, dummy persons will balance the problem. The data for a set containing all persons gets read from a file like this. The first half are the people in need and the second half are volunteers. The last X amount of people in need would be dummies in case of a surplus on the volunteer side. The last X amount of volunteers would  be dummies in case of a surplus on the other side. The example below shows a data set that was already balanced, so without any dummies. Based on the parameters NumberInNeed and NumberVolunteers the AllNodes Set containing all persons is de

3556
N
Click here to get AIMMS Community Edition
Terms & Conditions

Didn't find what you were looking for? Try searching on our documentation pages:

AIMMS Developer & PRO | AIMMS How-To | AIMMS SC Navigator