AMPL Modeling Language
https://groups.google.com/d/forum/ampl
A discussion and help group for AMPL, an algebraic modeling language for optimization problems of many kinds. AMPL lets people use common notation and familiar concepts to formulate models and examine solutions, while the computer manages communication with appropriate solvers.enRedundant fix/unfix/drop/restore commands
https://groups.google.com/d/msg/ampl/k9rzAorgBsQ/fsnABFPDCAAJ
Hi, I am solving a problem in an iterative way with the following structure and a unique model model mymodel.mod while {some_condition_not_respected} { #subproblem 1 restore necessary_constraints drop unnecessary_constraints fix fixed_variables unfix free_variables solve; #subproblehttps://groups.google.com/d/topic/ampl/k9rzAorgBsQ
Benoît MartinFri, 24 Feb 2017 09:38:03 UTCAMPL not generating output
https://groups.google.com/d/msg/ampl/hMFdHLWTtTU/Edkq8RGgCAAJ
Hi, I am a senior at The University of Illinois and am working on a 'Multiple Traveling Salesperson' code in AMPL. I am almost certain I am using a correct data and mod file and when I attempt to run the code, nothing generates, not even an error message. I attached a screenshot below of whathttps://groups.google.com/d/topic/ampl/hMFdHLWTtTU
Elizabeth TempletonThu, 23 Feb 2017 22:52:01 UTCRE: [AMPL 13608] Re: Timetabling problem. How to solve the error: "variable 'x' needs 2 subscripts, not 3"
https://groups.google.com/d/msg/ampl/H9CNY-CdjNM/333OgOJiCAAJ
I copied your model to the attached file and read it into AMPL without any errors: ampl: model WDS.mod; ampl: Can you attach the actual model file that is giving the error? Copying it into the email might have changed it in some way. Bob Fourer am...@googlegroups.com =======https://groups.google.com/d/topic/ampl/H9CNY-CdjNM
Robert FourerThu, 23 Feb 2017 04:10:47 UTCShortest path problem: road cost function of road usage
https://groups.google.com/d/msg/ampl/3KVZXl-_Vs4/OCsRkTqAAgAJ
Dear all, I'm facing a problem with the shortest path problem, which I have defined taking insipiration of what stated in AMPL book ch. 15 (see also https://groups.google.com/forum/#!topic/ampl/ziP84-AqdFs for previous questions). I would like to increment the cost of a road if that road ishttps://groups.google.com/d/topic/ampl/3KVZXl-_Vs4
GiovaPWed, 22 Feb 2017 11:06:01 UTCRE: [AMPL 13583] User-defined functions involving variables
https://groups.google.com/d/msg/ampl/2FJSG8HSCAA/8QFaBRBMAgAJ
You can use variables in an argument to a user-defined function, when working with any solver that relies on the AMPL-solver library to compute function and derivative values. SNOPT and IPOPT are solvers of this kind. When applying these solvers with a user-defined function, amplfunc.dll musthttps://groups.google.com/d/topic/ampl/2FJSG8HSCAA
AMPL SupportTue, 21 Feb 2017 19:10:04 UTCReducing AMPL solver print out
https://groups.google.com/d/msg/ampl/kTA_D0NH76I/jLOUu686AgAJ
In MOSEK AMPL interface we do something like i = Sprintf(hbuf, "MOSEK finished.\n%-17s : %s\n%-17s : %s\n", "Problem status",prostastr, "Solution status",solstastr); which cause AMPL to print out MOSEK finished. Problem status : PRIMAL_AND_DUAL_FEAhttps://groups.google.com/d/topic/ampl/kTA_D0NH76I
e.d.an...@mosek.comTue, 21 Feb 2017 13:51:38 UTChow to run an unrestricted XPRESS Academic Partner Program version within an unrestricted AMPL for Courses program?
https://groups.google.com/d/msg/ampl/zoK-qAxO3ro/Z37pUh4xAgAJ
Dear colleagues, The AMPL for Courses program allows my students to use an unrestricted version of AMPL during the period I teach them a course on modelling optimization. I ask my sutdents to look for real optimization problems, and to model them with AMPL Some of my students have been in ahttps://groups.google.com/d/topic/ampl/zoK-qAxO3ro
Jose FernandezTue, 21 Feb 2017 10:56:19 UTCPlease help me find out the the reason why these code does not work
https://groups.google.com/d/msg/ampl/sGKdA9qBVdQ/P140WagBAgAJ
Hey Rober, I have already rewrite the codes, however it still does not wotk. the reason is that param T is defined. I posted my model and data file. I hope you can help me to solve it. Model file: param T; # operation 6 months param a>0; #capacity cost OFhttps://groups.google.com/d/topic/ampl/sGKdA9qBVdQ
lidon...@gmail.comMon, 20 Feb 2017 20:26:35 UTCHow to use a .run file to read several Excel spreadsheets
https://groups.google.com/d/msg/ampl/MbLG6KdBnaA/0mINNKrvAQAJ
Dear all, I have a .mod file and I am using a .run file to read the parameters from a excel file. The problem is that I have almost like 30 excel files and I need to use the same .mod file to solve the 30 models with different data each one. I have the following: Problem.mod set Cities; andhttps://groups.google.com/d/topic/ampl/MbLG6KdBnaA
Alessandro Oscar Gilardino AriasMon, 20 Feb 2017 14:56:52 UTCProblem with user-defined functions involving variables
https://groups.google.com/d/msg/ampl/vchz5uezoY8/bAKnTqO_AQAJ
Hello, Recently, I wrote a model using some functions that are evaluated by an external program (REFPROP). To do so, I compiled my own library amplfunc.dll. My model works fine when I write my functions as expressions of parameters. In other words, my model is able to load the external programhttps://groups.google.com/d/topic/ampl/vchz5uezoY8
Cristina E.Mon, 20 Feb 2017 00:16:45 UTChow to use the if statement
https://groups.google.com/d/msg/ampl/pjD3Ywi-Mwo/LP8y9ytwAQAJ
Hey, I have a problem. I do not know how to use the if statement. V[j] is parameter. and the param value of E[j] is decided by the value V. Would someone help me to solve this problem? Thank you!!!!!!!! param v{j in 1..T}>0; param E{j in 1..T}=if v[j]=<5 then 0 if else v[j]=<10 thenhttps://groups.google.com/d/topic/ampl/pjD3Ywi-Mwo
Sun FeiSun, 19 Feb 2017 00:00:31 UTChow to use if statement
https://groups.google.com/d/msg/ampl/mBbtGFkgRPk/y7fcF99uAQAJ
Hey, I encounter a problem. I do not know how to use the if statement. V[j] is parameter. and the param valuse of E[j] is decided by the value V. Would someone help me to solve this problem? Thank you!!!!!!!! May I write like these? param v{j in 1..T}>0; param E{j in 1..T}=if v[j]=<5 then 0https://groups.google.com/d/topic/ampl/mBbtGFkgRPk
Sun FeiSat, 18 Feb 2017 23:36:42 UTCdouble declaration in dat and model file
https://groups.google.com/d/msg/ampl/JkANvJa8yQ0/0IpXWWZZAQAJ
Hi, I recently asked your support team a similar question, but was not precise enough. So let me clarify my question. Again, I have two files: a model file containing param n; param m; param Matrix { 1..n, 1..m}; …. and a dat file param n := 4 param m := 2 param Matrix :https://groups.google.com/d/topic/ampl/JkANvJa8yQ0
Benjamin PetersSat, 18 Feb 2017 17:03:13 UTCSubstitute complex expression as a dummy variable
https://groups.google.com/d/msg/ampl/xonePVOywMI/r-KB_tkwAQAJ
Hi, I have a very complex objective, some of the expression are repeating. Is it possible to substitute an expression with a dummy variable, without creating new constraint? I want to avoid that because my complex expression is non linear. Thanks Deepakhttps://groups.google.com/d/topic/ampl/xonePVOywMI
Deepak AgrawalSat, 18 Feb 2017 04:40:10 UTCAMPL recursive variable
https://groups.google.com/d/msg/ampl/oAIRPmqNt_M/usK4pPv-EQAJ
Hi everyone, I am having a problem trying to model a constraint on my problem and I would like to know if someone could help. I am sorry if this is a stupid question but I am totally new to AMPL. My objective is to find a tree structure starting from a given graph. I have already modeled a binaryhttps://groups.google.com/d/topic/ampl/oAIRPmqNt_M
SimonFri, 17 Feb 2017 17:48:47 UTC