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Hi, Community members, I'm excited to share a new online tool that has been developed by Dowon Lee, a graduate student in Industrial & Systems Engineering at the Univ. at Buffalo, with the generous support of AIMMS. tex2solver generates AIMMS code from LaTeX, or even pictures of an optimization model. In addition to generating AIMMS code, tex2solver also works with Python (using the PuLP package). I'm posting to the Community forum:To publicly thank AIMMS for their support of this project; To let the AIMMS user community know about the free tex2solver tool; and To ask for your assistance to help us test tex2solver.Regarding the last point, tex2solver is still in its development phase. Your feedback is very valuable to help us find bugs and add new functionality. Registration is easy (and free) at https://tex2solver.com. In return, we hope that tex2solver helps streamline your workflow from conceptualizing a model to solving it in AIMMS...like this: Happy optimizing,-chas
Dear all, I write on behalf of baobab soluciones, an AIMMS partner based in Madrid. Since the onset of the pandemics we have decided to support organizations and public authorities and offer our solution development services pro-bono for crisis relief projects. We were thinking route optimisation, workforce optimisation, workload management, load balancing between centres, for healthcare, quick response and critical supply chains. Quick, technically simple projects that will help take the most out of our exhausted common resources. So if you encounter a situation where we can be of assistance, please do not hesitate to contact us. Thank you very much, Julio
There are many impacts of COVID-19 that will be felt by Supply Chains in the coming weeks and months. As advised by McKinsey, in the next 2-4 weeks it is critical for companies to understand the exposure throughout their value chain, take actions to address anticipated shortages and ensure resources requirements to restart. Supply chain planning tools like AIMMS SC Navigator can be used to directly address many of these impacts and help businesses recover quickly from losses. We hope that this series of articles gives you some direction - and we welcome your comments and advice from experiences relating to these challenges. Understand Exposure Study 1: Anticipate Best- and Worst-Case Operations Scenarios Study 2: Inspect Demand Trends Anticipate Shortages Study 3: Identify Optimal Sourcing Locations Ensure Resource Requirements Study 4: Create Multiple Plans for Resource Utilization Study 5: Refine Capacity Smoothing Study 6: Accelerate Adoption of Relevant Customer Channels
Hello,Excuse the long explanation below. We are trying our best to make you understand the whole problem.I am a Masters student currently conducting research on the University Examination Timetabling Problem (UETP) using Binary Integer Programming. The problem is the same examination problem whereby it is to assign exams to suitable slots and venues accordingly to the requirements stated (hard constraints). The number of exams to be assigned, the number of slots available, the number of rooms available are declared as SETS. Also, the same goes for the parameters such as the capacity of each room, students taking specific exams, specific courses that requires 2 hours or 3 hours of exams and etc are known in advanced. We have successfully formulated all the constraints into BIP. Just to let you know that we are executing all models through AIMMS.Below are the constraints and objective functions involved in the model:Constraints: (numbers of constraint below will be used in the table give
I have run into the following problem, when I was trying to solve my MINLP model. The error massage is the following“OCTERACT error: [json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - unexpected end of input; expected '[', '{', or a literalWarning: Model status 13: Error no solution, Solver status 9: Error: Setup failure.Warning at line 1 in user-defined function section "MainExecution":Model status 13: Error no solution, Solver status 9: Error: Setup failure.OCTERACT error: [json.exception.parse_error.101] parse error at line 1, column 1: syntax error while parsing value - unexpected end of input; expected '[', '{', or a literalWarning: Model status 13: Error no solution, Solver status 9: Error: Setup failure.Warning at line 1 in user-defined function section "MainExecution":Model status 13: Error no solution, Solver status 9: Error: Setup failure.”The strange thing is that with another solver that my teacher got “BARON” it runs just f
t = time indexM = vehicle indexI = supply nodeJ = intermodal nodeI have a variable with (t,M,I,J) index which determines the number of units delivered to a specific node. However, I want to determine the time of delivery of each set of units as a separate variable. Thus, it’s like extracting t from the variables (t,M,I,J). How do I approach this?Thaank you!
Hey everyone,I'm working on a vehicle routing problem (VRP) project where the routing will involve more than one company, and customers may have orders from more than one company. So, the idea would be for the companies to collaborate with each other, and the customer would receive just one delivery.Given the larger set of available companies, I need to use in my constraints subsets that contain only the companies used for each customer. For example, if I have three companies, A, B, and C, how can I create a set with only companies A and B for customer I, another set with companies A and C for customer J, another set with only company B for customer K, and so on?My idea was to create a binary parameter, 1 when the customer requests that company and 0 otherwise. But can I write this parameter in the set definition? I thought about using if and else, but I'm having trouble because the parameter depends on two variables (customer and company) and the company set only on one (company).I'm
Dear colleagues,we are welcoming submissions to the invited session titled “Intelligent and data-driven decision making in green urban mobility” that is organized within the KES International Conference Sustainability in Energy and Buildings. The conference will take place in Santa Cruz, Madeira, Portugal, from the 18th to the 20th of September 2024.This is the Invited session link with details: http://seb-24.kesinternational.org/cms/userfiles/is05.pdfAnd this is the link to the conference website: http://seb-24.kesinternational.org/index.php Deadline for papers submission is: 13th May 2024 The conference proceedings will be published by Springer as book chapters in a volume of the KES Smart Innovation Systems and Technologies series, submitted for indexing in Scopus and Thomson-Reuters Conference Proceedings Citation Index (CPCI) and the Web of Science.For more information on the invited Session please contact: chiara.bordin@uit.no Kind regards,ChiaraAssociate ProfessorUiT, The Arctic
Hello!I have a MIQCP problem that I solve in AIMMS. I have tried to solve it both with Octeract and Gurobi. I solve the same problem with different data sets.For one of the data sets, the solving time for Gurobi is 319 seconds and the gap is 0%, while after 1 hour of solving with Octeract the gap is still 420%.For another data set, the solving time for Gurobi is 1834 seconds and the gap is 0%, while after 1 hour of solving with Octeract, the gap is still 9000%.Does this sound reasonable? I am not that familiar with how these two solvers work, but I thought it was a bit strange that the two solvers give very different results.Thank you in advance :)
I am building a multi depot multi vehicle transportation model. The model is running but gives 0 as optimal.I am just about to introduce the vehicles set and this is where i am having trouble now. I want each depot to have two type of vehicles. This is the best way I can get to right now. I want a set of vehicle type and a set of depot. I want to tell the model that each depot in this example: depot 1 has 2 scooters, and 1 truck, and depot 2 has 3 scooters and 1 truck. Is there a better way to do this, and how to resolve the error. Attached is my model.
Hi Everyone,I need help in implementing an optimization problem concerning the Vehicle Routing in AIMMS. I am currently indiciating the constraints for the mathematical problem. The index i and j is for the customers or nodes and k is for the vehicles. I now want to implement the constraint, that each vehicle can only leave the material-depot once. The material-depot i indicated by the value “0” for i or j. The mathematical formulation is now: sum x(0,j,k) <= 1In AIMMS it is indicated as follows: sum(j, x((0,j,k) <= 1)In this case, the index i is directly indicated with the value 0 for the depot but wenn I integrate this formulation in AIMMS, I receive a warning: “The symbol 0 is not expected”. How can I indicate this formulation in AIMMS in the correct way so that the system understands that “0” is the value for i? Maybe someone can help me.. Thank you in advance!! :)
First question:How do you make a variable have a consistent value across time? How to make a constraint that will make a variable equal to a previous value likevar(n,t) = var(n,t-1) Second Question:How can you model differently the 9 and 10th constraint?The main function of those constraint are a switch-like event. The constraints ensure that the binary variables for both set will be open, run for a number of time, and then stop.The main difference between the two are for the letter set, the binary variable should be open right from the start which means the binary variable must be equal to 1 at time = 1. How can you model this differently? Attached are the additional info about the AIMMS model.
Hello AIMMS Team, Trust this meets you well. I want to inject uncertainties into some parameters by using element parameter: "ep_robust" for "AllGeneratedMathematicalPrograms" An element parameter has been declared for the multiobjective optimisation. How do I bring in the ep_robust for the multiobjective function optimisation and individual objective functions optimisation? Your input here will be very helpful. The attached file can be used for the illustration. Thank you very much. Regards.
Hallo, ich habe 3 Produkte, von 14 Produzenten, die 3 Zielorten zugeordnet werden müssen. Allerdings kriege ich die richtige Verbindung im Modell nicht hin.Dazu habe ich 3 Sets. (K=Produkte, i=Produzent, a=Zielort)Anhand derersten Entscheidungsvariable wird berechnet, welcher Produzent wie viele Mengeneinheiten produziert. (Produktionsvariable)Diese produzierten Mengeneinheiten sollen dann an die drei Zielorte geliefert werden.Das Problem ist, dass ich der Bedarf am Zielort über k gesteuert wird. Aber meine Produktionsvariable steuert sich über i.Wie kann ich denn eine Verbindung modellieren, dass AIMMS versteht, dass i ausgeliefert werden muss, aber das Limit über k gesetzt wird?Bei Bedarf kann ich gerne Screenshots oder den Code einstellen.Danke vorab für jede Hilfe! LGYounes
Hello all together,Unfortunately I am a complete AIMMS beginner and can't get any further on my own.Can someone please help me to build this model (I have only the Academic License):Four products can be produced in a total of 10 locations (but not every product can be produced in every location).All products should then be transported to a fixed location.3 objective functions are to be considered simultaneously with different weights (minimize production costs, minimize CO2 emissions during production, maximize social impact due to production at each location).A few constraints should be taken into account, e.g. if 2 products come from the same location, the transport costs should be reduced, etc. This model should answer the question: how much of which product should be produced in which location? Thanks for your help!
First, let me introduce myself (as its my first post):Im and Industrial Engineer student making my end of master project studying the scheduling of a production plant. My tutor recommended me AIMMS to solve the MIP scheduling problem and, as you might have guessed none of us used this tool ever So far so good, i have found a scientific paper that solves my particular problem ( i dont think i can upload the paper, so I’ll upload only the good stuff)If AIMMS has a good thing its that it was easy (even for me) to introduce most of the constraints and definitions. So i made (most) of themBut theres one that particularly bothers me, restriction (2) and in a lesser way (7). This ones check the inventory stock at the the end of a certain T time, but if T=0, then it check It-1 (which it doesnt exist). And if T=1, it check It=0The thing is that I created a Parameter that holds the Initial Inventory and i wanted to keep as close as the formulation previously showed, so i went ahead and made some
Hello to everyone, i have the following problem i can not solve. So on the one side I have consumers that need a certain amount of energy at a time. On the other side I have a generator plant that produce green electricity. The Problem is, that the demand can not alaways be satisfied by the generators. For this I use batteries. The are charged, if there is more then enough energy available.The express this mathematically, I used a if then formulation: For the charging I use:Demand(t) - Generator (t) >= 0 → Battery(t) = Battery(t-1)*(1-self-discharge-coeffizient)+((Demand(t)-Generator(t))*efficiency_Inverter*efficiency_Battery)For the dischargingDemand(t) - Generator (t) <= 0 → Battery(t) = Battery(t-1)*(1 - self_discharge_coeffizient)+((Demand(t)-Generator(t))/efficiency_Inverter)Demand(t), Generator(t) and Battery(t) are variables.self_discharge_coeffizient, efficiency are parameters I do not have any clue how to solve the problem in AIMMS. If anybody could help me, i would be v
I am a novice. I'm working on a vehicle routing problem that considers soft time windows and fuel costs. I need to set a very large penalty value (b) so that it becomes a hard time window because I don't want to violate it. But the solution time will exceed 24 hours. Wondering how to reduce the solution time?The version used is 4.87.3.3. Other versions cannot be used due to research requirements.Thank you for your reply
Dear AIMMS team, I trust this meets you well. Thank you for all your support. My challenge is multifaceted. I am building AIMMS code to optimize hybrid energy system just as it is presented in the 'calc' sheet of the attached Excel file. The two AIMMS folders attached show how I have attempted to reproduce the 'calc sheet' functions in AIMMS, but below are the comments from AIMMS after running them: ''The definition of constraint 'Constraint_2(01)' contains an if-then-else statement with a variable in the condition, which cannot be handled by OCTERACT.'' ''The definition of constraint 'Positive_Energy_Difference_kW_definition(01)' contains an if-then-else statement with a variable in the condition, which cannot be handled by OCTERACT.'' All the column functions (in Excel 'calc' tab) are represented in AIMMS. It appears the way I have written the conditional statements in the two AIMMS folders is not allowed. Kindly assist further. Please note: The AIMMS data file for both AIMMS fol
Hi all, I would like to seek clarification regarding the disparities between MIP (Mixed Integer Programming) and RMIP (Relaxed Mixed Integer Programming) solvers. While I understand that RMIP converts integer variables into continuous variables, I would like to explore any other significant dissimilarities between these two solvers.Specifically, I am encountering fluctuations in the results of one of the variables when utilizing the MIP model as shown in the picture below. Despite the absence of any constraint-related issues, the values exhibit variability instead of remaining constant. Conversely, when employing the RMIP solver, the values remain consistent throughout (as presented in picture below). I am keen to understand the cause behind these fluctuations and any significant disparities between the MIP and RMIP solvers that could potentially explain this behavior. Any insights, explanations, or suggestions on how to address these fluctuations would be greatly appreciated too! Than
Hi,I am solving a huge MIP (481707 integer variables). I set the relative gap to 0% from CPLEX MIP settings. With such a huge model, the solver should take quite some time to solve. Just after 287466.11 sec (3.3 days), the model stop running and the solver status says 'Terminated by solver' why the gap is 1.27%. Why does this happen? I am attaching a screenshot. I'll appreciate any ideas on this. Thanks !
Dear AIMMS team, Trust you are doing well. I recently installed AIMMS version 4.94.3.3 and I only found two solvers namely: CBC 2.9 and IPOPT 3.11. I tried adding more solvers to it through the solver configuration but proved abortive. How can I add the following solvers to the version.Conopt, CPLEX, Baron, CP Optimizer, Gurobi, COPT, MINOS, ODH-CPLEX, OCTERATH, PATH, KNITRO, NETSOL. I have also attached the messages I am receiving. Thank you.
