Optimization Tooling

Hello everyone,  I have an Element Parameter PredecessorOperations(i_operation) that holds the value of the operation that has to be executed before i_operation. With the following statement i want to check if the EP has a value or not:  if (val(PredeccesorOperation(i_operation)) = 0) then….endif; However this only works if all values of the Ep are empty. If any operation gets assigned a predeccesor (e.g. Operation1) then i get the error: Cannot compute the value of string “Operation1”. If I would casually formulate the code it would look like this: if( PredeccesorOperation(i_operation) is empty ) then ….endif;So my question is: What operator do I need to use in order to check if the parameter has any value or no value assigned? I am thankful for any advice you might have. With kind regardsAndrew 

Hi folks,I’m doing some tutorials in AIMMS and I find that the data exchange library is missing from my AIMMS version. Can anyone point me how to install it? This is what I currently see: ThanksLS

Hi everybod,I have a quick question and hope you can help me.I calculate in my model the optimal stock level depending on the period and szenario specific demand.The inventory level is defined as follows: Inventory_PreviousPeriod + ProductionQuantity_CurrentPeriod (also a variable) - DeliveryQuantity_CurrentPeriod.How is it possible to preset the variable stock for the first period to a fixed inital value (in this case the opening inventory)?I would be very grateful for your answer!Best ragards, Hans

Hi everyone, I need to make a simulation in Aimms to simulate the mechanism on the following picture:   Order Release Mechanism I have no problem in declaring all the sets and parameters, but my main 2 problems are too make the periods pass correctly and repeat all processes in the periods and too update the loads and sets at the right points in time.  I have too do this via simulation so without an objective function thats also something that throws me off cause i cant use a Mathematical Programm so solve this.  Maybe the solution is simple but i havent ever worked with Aimms and that is a very big project for me, which is also very urgent so i really appreciate any help i can get.  With kind regards AlexPS.: The programm i made so far is attached as a zip-file. Maybe u can tell me how i need to adapt it to make it work. 

Dear all,  I am fairly new to Aimms, but for my thesis i need to solve a model in Aimms that has no objective function. Its like a scheduling problem, but it must not be optimization based.  So i have most parts of my Model but i dont no how to implement it since i cant use constraints and the solver. One Idea i had was to just make an irrelevant Objective function, let the Solver solve it and have my other parameters (Which Order goes to what station at what time and what is the capacity at each station) as results of the simulation. Would this work or is there any other way i can set this up properly? Thank you in advance. With kind regards, Andrew

Hi AIMMSians,I have formulated an NLP model with around 2500 variables and it is non-convex. When I solve it using IPOPT, I get the error “Intermediate Infeasible, terminated by solver”. When I use CONOPT as solver, I get same error. Analyzing the listing iteration log files, it reveals that solver labelled the solution as infeasible because the convergence is too slow as demonstrated by message in the end of listing iteration log “Convergence is slow and a derivative is discontinuous”. Please note that sometimes, the same model reached a “local optimal” with sensible values for the variables. With some nice information in AIMMS documentation, forum and webinar, I have tried scaling option, good initial points (which are not possible in every case) and a bit of reformulation by removing some variables acting as intermediate variables between two variables to calculate some values. None of these options have proved any change in the results. Any idea or word is highly appreciated. Thank

Dear Community, we want to be able to edit multiple cells of a WebUI table, like using shift or ctrl to celect the cells and later edit them at once. We would like to be able to use copy paste as well. We coundn't find any resources describing a way of enabling these functions. If you know how to do it, or have some helpful resources please share it with us.

Hi everyone,I have been trying to call an AIMMS (academic license) procedure from python although this doesn't seem to work. I got the following code from another thread, which seems to work with a paid license. I also saw on another post that the academic licence might have some limitations in this regard. Is there an API in another language, were I can make Python wrapper around this other language?orIs it possible that AIMMS internally allows to run scripts in some language, in which case a script can be built  in such a way that they exchange model parameters/inputs/results with the outside world? Best regards,

Good day people….i am new to AIMMS. I want AIMMS to read from a dat file but it keeps giving me the  statement “The symbol ";" is not expected.” The content of the dat file is  COMPOSITE TABLE:G  M P R_M R_P!-------------10 8 4 10  15 ; after removing the symbol ; it pops up another error which is ‘The symbol "15    " is not expected.’after removing 15, it pops up another error which is ‘The symbol "10     " is not expected.” Is there something i am not getting right on how to structure the contents in dat file. Kindly help please.  

Hi All,I want to compare two scenario for better understanding of output data. And i want to do it from WebUI.Help me to built my Model with such capability. Thanks

Hello,I’m a student who is using AIMMS for my university project and I am using a academic license.Yesterday i started receiving the error message “Error in AIMMS license - Inconsistent system date” during the solving process.It happens typically while solving my model for some time (around 1 hour)AIMMS gives me the choice between exiting now without saving or exit later with a timer of about one minute to save my project. Has any one encounter this problem and knows a soulution? 

Hello, For a university project we use AIMMS to solve a model, we also would like to use the WEB UI, however after building the WEB UI it does not save. Why does it not save, is it because we have an academic license? In the AIMMS model the module 'AIMMSWEBUI [read only]' has the property no save, however since it is read only, we are not able to change it. Is there a solution for this problem?Kind regards!

Hello everyone!Is it possible to remove the default stroke color (black) when user clicks or selects any node/location which has already defined stroke color? This is so that the customized stoke colors (defined in model) for the nodes remain functional even when any node is selected. I see customized stroke colors appear back when clicked twice on any node.In my case, by clicking on any location, the stroke colors are turned off and default stroke color black turns on. By clicking on same location again, we can see all stroke colors for potential locations(orange) and optimal location(red). Please find attached screenshots for reference.  Thanks in advance for help on this case!

Hello everyone,  In the problem that I have to solve, I have got two sets: j (=1, …, 5) and k (=1, …, 9). I also have a parameter: parameter(j,k) and I want that j begins from 2 (and not from 1) for this parameter. How do I put it in AIMMS? Moreover, in my objective function I want to minimize the sum of my costs but for j >= 2. My current formula looks like this: sum[j, 200*W(j)]     with W(j) a variableHow do I specify that I want j to be larger or equal than 2? Thank you

Hello, I’m trying to solve my thesis model but there has been message about infeasible solution. ‘’Warning: After zero iterations CONOPT 4.1 concluded that ModelNew is locally infeasible.’’ I obtained some data in the listing file but the model is still showing infeasible. I would appreciate if anyone could help me to solve the infeasible problem.As attached is the zipped file of my model (Model New.data is the data file of my model).Thank you in advance.  

Hello everyone after formulating my model in AIMMS, the solver tells me that my solution is not feasible I tried to simplify my model by removing some binary elements but I still get the same answer. I think the problem must be somewhere in the flow conservation or capacity constraint, could someone take a look at it and tell me the problem.I also have a duplicate column warning message I think it's from my bad formulation of the problem if someone can also tell me how to fix it thank you very much.Ps: I saw that these questions were asked regularly but I took the liberty of making a new topic because I would like to have an answer specific to my case and I could not solve my problem by reading the other topic. 

Hi, I have a String Parameter with index domain “i” called “ModPrefix” containing prefixes of modules within my project. Each of this modules has a variable with the name “Q”. Now, I would like to access these variables within the definition of a Node called “FacilityNode” likeNetOutflow = ModPrefix(i)::QHowever, this leads to the errorThe identifier "Q" has not been declared, but it is declared in the modules [...].where I replaced the names of the modules with “[...]”. My idea of a workaround was an if-then-else-statement likeNetOutflow = if ( ModPrefix(i) = "prefix1" ) then prefix1:Q elseif ( ModPrefix(i) = "prefix2" ) then prefix2:Q else 0 endif;in the case of two modules with prefixes “prefix1” and “prefix2”. However, I would still like to know if there is a way to circumvent it-then-else-statements, since they become ugly in the case of many modules.  

Hi! I’m doing a supply chain optimization using AIMMS for my master project and I have a problem with my binary determinant variable as well as the result error computed. Since this is my first time using AIMMS, I am not sure on how to debug it.The constraint of my binary is X(i,l,g,g2) + X(i,l,g2,g) ; where g≠g2.After I run the program, it saysWarning: The rows "TransportationBinary(liquid hydrogen,truck,g1,g3)" and "TransportationBinary(liquid hydrogen,truck,g3,g1)" are equal in the generated mathematical program "MinimizeDailyCost".  This may lead to non-unique shadow prices.  For more information regarding potential causes and consequences, see the help associated with the option "Warning_duplicate_row". Can anyone help me explain what is the problem? I am also confuse on which section to declare the g≠g2 in the transportation constraint (g represents the grid squares/ supply demand location).Appreciate your help!

Dear community,I just rolled into AIMMS, so the application is very new to me.I came across a problem with implementing constraints into my model. You can see the specific constraint and my model in the attached illustrations. After filling in the definition for the constraint, an error popped up, saying "The scope of index "cred" has not been specified.", where "cred" is the index domain for the variable "CarbonCredits".I already tried to re-implement the whole model, change the index and i messed around with different brackets in different positions. Nonetheless, i kept getting the same error.I would appreciate it if someone could help me out. A picture (of an example) on how the definition of this constraint should look like would be phenomenal as well.Thanks in advance, Stijn

I am a student and have been using AIMMS for roughly a year already. When I tried opening AIMMS today, the following occured: Logging on to AIMMS License Server failed: No logon response from server.Another user had the same problem, however the solution to that post didn't work. Did the license expire or is something else the problem?   

Hello everyone, this is my error message.Warning: After zero iterations the preprocessor of CPLEX 20.1 concluded that MinCost is infeasible or unbounded.I think the problems lays in my constraints.Production_workcenter is 100% incorrect but i’m not sure how to use the subset allowed_product_per_workcenterAre there other problems ?Thank you Marc

Hi!The model aims to optimize the energy flow in my superstructure and minimize the cost. Most of the data in the listing file show that the status is superbasic and some of them are superbasic, at bound. Here is the message showing on top of the listing file.CONOPT 4.1 constructed the following irreducible infeasibility set (IIS).The IIS consists of 1 constraint and 1 variable.HWH(6) .. [ 9 | 273 | IIS ]    + 1 * Techflow(HW,6) - 0.800 * NGflow(HWH,6) = 0 ; (lhs=-25630, scale=3600000) ****    name              lower   level   upper   scale    Techflow(HW,6)     -inf  -25630     inf 3600000    NGflow(HWH,6)         0       0     inf 3600000  <--- pivot columnThe constraint is stated like this:HWH(t):Techflow('HW',t)=EfficiencyNG('HWH')*NGflow('HWH',t)Attached is the zipped file for my model. I would appreciate if anyone could help me to solve this.

We currently work on using the AIMMS Unit Test Library for all our tests instead of manually checking the success of a test run with the help of binary parameters. In this context, we thought of emptying all parameters before the run of each unit test to ensure that the run sequence of tests does not impact the outcome. We noticed that emptying all identifiers also leads to emptying parameters with initial data. Is there a way to reset all parameters to the state before we ran the unit tests or at least to their initial data? Kind regardsSandra