Xpress-MP Google Group

Stochastic Programming Module

2009-06-07T17:07:41Z

Hi all,

I have been using the "mmsp" module for solving a multistage recourse
model. I have been searching on the website to find the underlying
algorithm(s) that are used by this module. Can anyone help?
I believe that the recourse model is reset as a large scale LP
equivalent en solved accordingly. Is this correct?

E-1013 Infeasible constraint

2009-05-26T17:39:55Z

I'm getting the error E-1013 Infeasible constraint in my model with
code on line 78: "sum(l in T)M(i,l,1)*l+sum(j in E,l in T)P(i,j,l,1)
*l>=Es(i)" How can I solve this?

This is the code for my model=

model Carpool
uses "mmxprs"; !gain access to the Xpress-Optimizer solver

!optional parameters section

XPRS_TOP and XPRS_LIN

2009-05-24T17:08:28Z

Hello

What is the difference between XPRS_TOP and XPRS_LIN?

Thanks

XpressMP on Leopard

2009-05-22T14:07:37Z

Dear Madam, Sir

may I ask you whether there is any chance to see XpressMP running on
Mac Os X in the next months?

I do not refer explicitly about the porting of Xpress-Ive (which
however make the development really easy), what is
really important to me is the possibility to use XpressMP on mac os x

Converting a string to numeric?

2009-05-11T18:32:33Z

Hi guys

I need some help. I have a file with both numeric and character data.
and i imported these to a 2d array(of type string) in mosel.

Now, this is what I wanna try...

Can I access a column from this array and then extract the numeric
value (in effect i wanna convert the string type info to numeric data

Re: PLZZZZZZZZZ HELP

2009-05-11T17:23:06Z

I am not sure if I did understand the question... but if what you want
is to load an array from a dat file you can do it by means of for
loops as:

forall(a in 1..A,b in 1..B) do
read(D(a,b))
end-do

You do not need to strictly start from 1.

Interpretation of the Solution

2009-04-15T16:59:59Z

Hi,

I have used Xpress in my dissertation and must interpret my results
properly. In the book as well as in the net I could find nothing the
fitting, for this reason the last attempt is to write here.

Please, explain me how to interpret the Rows (constrains), Columns
(variable), Non-zero elements as well as Simplex iterationens.

xPress Mosel IVE!

2009-04-14T13:00:24Z

Hello!

I'm a greenhorn in programming and modelling and I hope somebody could
help me!

I have the following problem with xPress Mosel IVE:

I have a linear program with the following side condition: (Transport
condition)

y1l >= LB1 or y1l = 0

l ... stands for distribution center or consumer

Optimization Libraries Student Version

2009-04-02T20:43:51Z

Hi there,

I was wondering if it is possible to obtain the Xpress Optimization
library for UNIX operating systems as a student version? I just need
the optimizer (and a mex interface), no fancy IDE.

Thanks,

Max

Xpress MP student edition can do sensitivity analysis?

2009-03-31T15:36:50Z

Good afternoon
I have a doubt about the student version of xpress MP. I want to know
if the student version of xpress MP can do sensitivity analysis?
Best regards
André Soares

sensitivty analysis on the student edtion

2009-03-30T17:14:00Z

Good afternoon

I have a doubt about the student version of xpress MP. I want to know
if the student version of xpress MP can do sensitivity analysis?

Best regards
André Soares

Information about ucbdata

2009-03-17T11:05:07Z

Dear all,
We are trying to lead the branching variable in the B&B performed by
XPRESS.
To this end, we have found the callback function XPRS_CB_CHGBRANCH
that in
principle allows to choose the new branching var. by means of the
ucbdata
procedure.

Our question is about the parameter of this function. In principle,

LP gone horribly wrong

2009-03-08T17:41:03Z

Hi there!
I'm trying to solve the following problem: I've got five production
plants and numerous customers and I have to decide what amount of a
product should be produced by which plant to serve the needs of the
customers.

As I'm new to the XPress MP (Student version) I implemented that in

How to know when the B&B has found an Integer solution

2009-03-03T10:26:50Z

I am working in a Branch and Cut algorithm.

I have to apply a procedure to add cuts when but only when the node is
an integer solution. Somebody knows how to determine if one node is
and Integer solution?

Kind regards

Stacked column

2009-02-06T14:58:29Z

Is there anybody that can help me graphing stacked columns (thats what
they call it in MS excel) in Xpress (IVE)? It is a power modelling
problem where I want total power production in each period as columns,
and the different power generators as different colors in the columns.
For example if power production in period 1 is 20MWh coal and 30MWh

getsolatnode

2009-01-28T09:10:51Z

Hi all,

I have a multistage mixed integer recourse model in xpress. In order
for me to evaluate my solutions I would like to have a print function
or whatsoever, to get my results at every node of the scenario tree
for different decision variables.
In order to do so I can call some solutions with the getsolatnode()

MAX_COMPUTATION_TIME does not work?

2009-01-26T23:09:25Z

Hi,

I have a mosel model which I want to test on several instances of a
problem. Therefore, I decided to set a time limit to 1800 seconds,
after which the best solution so far shall be put out.
I tried the following code line:
setparam("MAX_COMPUTATION_TIME ", 1800)

but it does not seem to work, the computation time is at 4800s right

Mixed Integer Linear Programing Duality

2009-01-26T18:07:12Z

Hi all,

I have been using XPress-MP to solve mixed integer linear problems but
unfortunatelly can't get the dual values of the constraints, since
getdual command is not working for some reason with integer problems.
Does anybody know how to handle this?

Thanks,

need advice Xpress-SP

2009-01-25T05:34:14Z

Hi,

I am very new to Xpress-MP. I have a stochastic mixed integer linear
problem to solve. As I read on website, seems like it can be solved
using Xpress-SP (as I need some scenario generation) which is solver
for stochastic problems. But I have no idea how to use Xpress-SP. It
has been mentioned that there is Xpress-SP reference manual but I have

Help needed in some modelling issues

2009-01-24T13:44:37Z

Hi all,

I just started in Xpress-MP and during the programming of my MIP I
came accross a few things that I cannot explain. The model runs
without any error messages, but does not produce any results. I think
this is caused by assigning (actually not assigning) initial values to
my variables.

Problema de Optimización con Funcion Objetivo con Logaritmos

2009-01-06T03:12:42Z

Hola!

Quisiera saber si existe alguna manera de que Xpress-MP resuelva
problemas cuya función objetivo sea el logaritmo de la suma de dos
variables de decisión.

Gracias
PAOLA

combining Image to Xpress Model

2008-12-20T02:05:19Z

Hi, folks,

I am building several location models and desires to embed maps within the
Xpress, has any one tried it in IVE ? or do I have to write a GUI separated
and use data file to link the data and solutions?

Please let me know.

Xinhui Zhang, Ph.D.
Assistant Professor of Industrial Engineering

?45 error

2008-12-18T23:16:01Z

Hi everyone

I've been running into some problems with mosel. I leave my program
running overnight and when I check on it inthe morning, I keep getting
the same error message. Here's the error message with the end part of
the log file:

Node BestSoln BestBound Sols Active Depth Gap

help with removing objects in a set

2008-12-18T15:55:27Z

Hi all,

I have been asked to solve the following problem in a better way by
the use of a greedy algorithm. It is called a vertex cover problem,
some of you might have heard of that one. You have to keep removing
elements from a set until it is not a vertex cover anymore. How can I
put this in MOSEL? The Mosel code looks loke this at the moment:

Conditions for mpvars in constraints, directly or indirectly

2008-12-09T22:11:28Z

Hello,

I have the following problem

declarations
PathCost: array(100) of real
PathLoad: array(100) of mpvar
.......
......
end-declarations

.......constraints etc.......

objective is TotalCost = sum(l in 1..100) PathCost(l) * PathLoad(l)

In reality the PathCost for each path depends on its load. The higher

Using VB .NET with Mosel - Reading records

2008-12-08T23:00:09Z

Hi,

My first post in this forum. Hope this group is still active.

I have a Mosel model built and compiled and it works fine without any
issues. But I would like to call and run the model from within
VB .NET. I am actually able to run and solve the model as well using
the Mosel .NET reference library (xprmdn.dll). But my problem is with

student version

2008-11-18T08:57:26Z

Hi,
I am getting started with Xpress-Mosel.
I am not sure if in the student version can model a Non Linear
objective Function or not?

Is there anyone who can help me?

Thanks
Elham

Infeasible solution

2008-11-15T00:24:45Z

Hi,
I am new to Xpress, I have a model which is giving me an infeasible
solution. Therefore, I tried introducing a supplemental variable (x1)
so as to satisfy the constraints. But now the model is giving me a
compilation error. I have been trying to resolve this problem for 2
days. I guess I am doing something wrong while coding it. I will

Abs constraint problem

2008-11-10T09:58:40Z

I need to state some constraints like this:

I linearized them by using binary dummy variables...Isn't there a
better idea to state this without using dummy variables 0/1 in xpress-
ive?

Thanks.

Student version not a valid Win32 application

2008-11-07T09:56:49Z

"Not a valid Win32 application." error in Xpress-MP Student Edition

If you experience that message when you attempt to install
"student.exe", it could be attributed to you were running antivirus in
the background say "Resident Shield" in AVG Free 8.0

You need to stop it when you are downloading the installer and when

Question on evaluating

2008-10-30T15:47:02Z

I'm evaluating XPress, and I'd like to know, how to use maximum RAM
for the model, because we're going to solve very large-sized problems.
Can anybody help me, please?

Issues regarding sequentially solving several problems ..

2008-10-27T15:06:47Z

I need to solve many instances of an MIP model ..

If I load the problems one by one, I get one solution .. but if run
the a program that automatically reads, sovles and writes the output,
the solution is different (worse), although correct..

Any ideas why this is happening?

here's the code:

lack of mmnl module in student version

2008-10-23T15:01:54Z

hi,

I have university assignment to solve that requires non linear
constraints. Unfortunately I can't find mmnl module in my student
version.
Does anyone know how can I obtain one?

--
greetings,
Piotr

Infeasible Constraint

2008-10-01T16:34:44Z

I have my model almost completely debugged except for one last error -
infeasible constraint. I know that technically, it is not infeasible
as I have been able to run the same model with other software (LINGO)
with no problem. I know the typical checks for this, but is there a
way to see the values going into the constraint so that I can see

Using double or triple sums in the objective function.

2008-09-29T15:40:03Z

I am new to using Xpress-MP and need some help. I cannot find any
examples in the documentation or in the program itself of how to code
(in Mosel) double sums (or higher). I thought it would be like:

sum(i in SET1) (sum(j in SET2) cost(i,j))

But I keep getting syntax errors. My actual function is much more

abs function at objective function

2008-09-26T07:42:08Z

How to make the following term in Mosel language?

Maximize |x - y|

I tried

Maximize abs(x-y)

but, it didn't work.

plz help me.
Thanks.

Optimality Gap

2008-09-19T05:17:13Z

Hi All~

I have a question when I am solving a large model.
When we use XPRS_MAXTIME to stop the optimizer after running certain
amount of time, is there a way to return the optimality gap between
current solution and the true optimal solution? Thanks a lot for the
help.

Peng

Is Student version available for Linux operating system?

2008-09-12T06:27:35Z

Dear All,

I am a PhD student at IIT Bombay. I am working on optimization and I
use Linux operating system.
please tell me that Xpress-MP Student version is available for Linux
operating system or not ?

Thank you
-Sekhar

Re: Help needed urgently!

2008-09-30T16:27:34Z

What error message are you getting?

Using the mod function

2008-08-19T15:24:49Z

Hi All,

I was curious if the mod function could be used on variables. I've
tried and my IP doesn't seem to compile. It keeps throwing the error:
"E-112 Numeric expression expected for operator `mod' ". Does anyone
know for certain if it's because I'm using a variable? Thanks for the
help!

parameter initialization in C#

2008-08-07T00:02:33Z

Hi,
I'm trying to pass some input parameters into Mosel from C# but 'm
running into some trouble. I'm using the mmexdrvs.cs as an example and
I can initialize a first set of variables but I'm having trouble
initializing a second group of them.

I have in a Mosel file:

parameters
INIT_FNAME='in.txt'

Warning W-0

2008-07-31T16:25:31Z

Hello,

I install the current version of Xpress-MP for students, and I get
this message when the program starts:

"(Line: 0, Col: 0) : warning 0:XPRS (Warning): Wrong XPRS version
number 0 (expected: 19)"

Then it shows : "XPRS: Error when loading the problem." when I run any
model.

I have installed this student version in 2 PCs, and I get the same

make a dll in mosel

2008-07-21T15:53:50Z

Hi! I need some help please. I need to create a dll from mosel. I
don't know how to do it or even if it's possible. Thanks

Running time error

2008-07-05T08:52:42Z

Hi every one,
I am running a problem for my project using Xpress-MP. Every time I
run it for about one hour, the program indicates this kind of error:
An unexpected exception occurred in Model/Optimizer.It is UNSAFE to
continue. please save your work and restart.
I have read someone's post in this group advising to review some

How customize the branch and bound algorithm?

2008-06-19T09:12:09Z

Sorry,
i need to introduce a heuristic procedure for each node of the branch
and bound tree. The problem is that in my procedure i need to make an
optimization with minimize(XPRS_LIN,""), but it's impossible if the
optimizer already running. How can i do? I read about EMOSL, but i
didn't find it.

errors running models

2008-06-18T12:41:16Z

I'm using Model 2.2.0, mmxprs version 1.6.2, mmive version 1.18.5
I'm finding that programs that used to run under previous versions now
don't. I've changed arrays to :, when initialised from file. Some of
the arrays are initialised successfully, but there is an "error runing
model or execution interrupted" and no other indication of what is

.NET wrapper throws an BadImageFormatException

2008-06-16T18:32:17Z

Hi,

I tried to use the xprsdn.dll library in a visual studio 2005 project,
but every time i try to call a function (i.e. Init(string) or Init())
in the optimization namespace, I get a System.BadImageFormatException .
What am I doing wrong?
My System is a Vista x64 Business, could this be a problem?

Help with using xprs.dll

2008-05-20T15:01:00Z

I am writting a program that needs to call the methods from xprs.dll
file; i.e. XPRSlicense, ....
This program is written in C#, how can I accomplish this?

getsol(x:mpvar) -> returns wrong value!

2008-05-18T14:32:12Z

Hi!

I rerun an optimization model several times. To check the results I
calculate the objective value "manually", by summing up all terms of
the objective function. For example: One part of the objective
consists of the sum of setup costs:

sum(i in 1..I, j in 1..J, t in HR) ( X0(i,j,t) * SC(i,j) )

Java, but using a library Xpress

2008-05-16T23:41:17Z

Good night 4 all,
I got the Xpress-Student and I´d want to designe a java program that
invokes a library Xpress. How can I do it? I didn't find neither
the .jar file in web nor instructions of how to use it.
Thanks,

Jonata