[FlopCpp] wrote first flopcpp model. have a lot of questions
Tim Hultberg
Tim.Hultberg at eumetsat.int
Tue Dec 1 11:42:41 EST 2009
Hi Mario,
here are some answers:
1. Yes, that is possible.
2. You can output the problem in MPS format or 'lp format'. See the recent mails on the list about how to do this.
3.
4. You cant. Flopc++ can only be used to model LPs and will not allow you to divide with an expression involving decision variables.
5.
6.
void MP_constraint::display(string s) const {
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cout<<s<<endl;
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if (offset >=0) {
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for (int i=offset; i<offset+size(); i++) {
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cout<<i<<" "<<M->bl[i]<<" "<<M->rowActivity[i]<<" "<<M->bu[i]<<" "<<M->rowPrice[i]<<endl;
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}
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} else {
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cout<<"No solution available!"<<endl;
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}
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}
I know I didn’t answer everthing, but I have to go now..
Tim
From: flopcpp-bounces at list.coin-or.org [mailto:flopcpp-bounces at list.coin-or.org] On Behalf Of Mario Rappi
Sent: Sunday, November 29, 2009 2:47 AM
To: flopcpp at list.coin-or.org
Subject: [FlopCpp] wrote first flopcpp model. have a lot of questions
First I include the model, then the output, and at the end the questions:
*****model************************
// $Id$
#include "flopc.hpp"
using namespace flopc;
#include <OsiClpSolverInterface.hpp>
int main() {
MP_model &model = MP_model::getDefaultModel();
model.setSolver(new OsiClpSolverInterface);
model.verbose();
enum {storeA, storeB, storeC, storeD, numS};
enum {Input1, Input2, numI};
enum {Output1, numO};
MP_set S(numS); // Stores
MP_set I(numI); // Inputs
MP_set O(numO); // Outputs
MP_subset<2> Input(S,I);
Input.insert(S,I);
Input.display("Input");
MP_subset<2> Output(S,O);
Output.insert(S,O);
Output.display("Output");
//this will be easier with an array??
MP_data InputVal(Input);
InputVal(storeA,Input1)=1; InputVal(storeA,Input2)=3;
InputVal(storeB,Input1)=3; InputVal(storeB,Input2)=3;
InputVal(storeC,Input1)=4; InputVal(storeC,Input2)=2;
InputVal(storeD,Input1)=3; InputVal(storeD,Input2)=1;
MP_data OutputVal(Output);
OutputVal(storeA,Output1)=1;
OutputVal(storeB,Output1)=1.5;
OutputVal(storeC,Output1)=2;
OutputVal(storeD,Output1)=1;
MP_variable x(I), y(O);
x.lowerLimit(I)=0;
y.lowerLimit(O)=0;
MP_constraint efficiency(S);
efficiency(S) = sum(I, InputVal(S, I) * x(I)) <= sum(O, OutputVal(S, O) * y(O));
minimize( (sum(O, OutputVal(storeB, O) * y(O))) - (sum(I, InputVal(storeB, I) * x(I))));
efficiency.display("constraints");
x.display("x");
y.display("y");
cout<<"Test dea passed."<<endl;
}
*****model end************************
*****output************************
Input
Output
FlopCpp: Constraint
0 1 0 0
1 1 0 0
2 1 0 0
3 1 0 0
0 2 0 0
1 2 0 0
2 2 0 0
3 2 0 0
0 0 -0 0
1 0 -0 0
2 0 -0 0
3 0 -0 0
FlopCpp: Number of constraint blocks: 1
FlopCpp: Number of individual constraints: 4
FlopCpp: Number of variable blocks: 2
FlopCpp: Number of individual variables: 3
FlopCpp: Number of non-zeroes (including rhs): 12
Objective
-1 0 0
-1 1 -0
-1 2 -0
FlopCpp: Generation time: -2.64274e-19
Clp0000I Optimal - objective value 0
Clp0032I Optimal objective 0 - 0 iterations time 0.002
FlopCpp: Optimal obj. value = 0
FlopCpp: Solver(m, n, nz) = 4 3 0
constraints
0 -1.79769e+308 0 0 -0
1 -1.79769e+308 0 0 -0
2 -1.79769e+308 0 0 -0
3 -1.79769e+308 0 0 -0
x
0 0
1 0
y
0 0
Test dea passed.
*****output end************************
*****Questions:******************
I would like to define a set A that includes all members of O and I and then derive O and I from A.
This is what I am thinking in GAMS terms:
A / Input1, Input2, Output1 /
O(A) / Input1, Input2 /
I(A) / Output1 /
Is this possible?. I thought it would allow me to write the model more easily (but may be not)
*******************
I tried to display the constraints but I didn't get what I was expecting (the actual mathematical expression). Is it possible to see the constraints in any other way?
*******************
When I compile I get the following two warnings. Should I be concerned? How do I fix them?
c:\program files\coin-flopcpp\flopcpp\src\mp_set.hpp(259) : warning C4267: 'return' : conversion from 'size_t' to 'int', possible loss of data
c:\program files\coin-flopcpp\flopcpp\src\mp_set.hpp(258) : while compiling class template member function 'int flopc::MP_subset<nbr>::size(void) const'
with
[
nbr=2
]
c:\program files\coin-flopcpp\flopcpp\examples\dea.cpp(21) : see reference to class template instantiation 'flopc::MP_subset<nbr>' being compiled
with
[
nbr=2
]
c:\program files\coin-flopcpp\flopcpp\src\mp_set.hpp(243) : warning C4267: 'initializing' : conversion from 'size_t' to 'const int', possible loss of data
c:\program files\coin-flopcpp\flopcpp\src\mp_set.hpp(232) : while compiling class template member function 'void flopc::MP_subset<nbr>::insert(const std::vector<_Ty> &)'
with
[
nbr=2,
_Ty=int
]
*******************
The objective function that I really want to use is
maximize( (sum(O, OutputVal(storeB, O) * y(O))) / (sum(I, InputVal(storeB, I) * x(I))));
But it doesn't compile, I get this error:
c:\program files\coin-flopcpp\flopcpp\examples\dea.cpp(51) : error C2678: binary '/' : no operator found which takes a left-hand operand of type 'flopc::MP_expression' (or there is no acceptable conversion)
c:\program files\coin-flopcpp\flopcpp\src\mp_constant.hpp(141): could be 'flopc::Constant flopc::operator /(const flopc::Constant &,const flopc::Constant &)'
c:\program files\coin-flopcpp\coinutils\src\coinpackedvector.hpp(483): or 'CoinPackedVector operator /(const CoinPackedVectorBase &,const CoinPackedVectorBase &)'
c:\program files\coin-flopcpp\coinutils\src\coinpackedvector.hpp(583): or 'CoinPackedVector operator /(const CoinPackedVectorBase &,double)'
c:\program files\coin-flopcpp\coinutils\src\coinpackedvector.hpp(625): or 'CoinPackedVector operator /(double,const CoinPackedVectorBase &)'
while trying to match the argument list '(flopc::MP_expression, flopc::MP_expression)'
I am using MSVCPP, I read of some problems specific to VCPP so I tried the same in Linux(I think it is build-essential in Ubuntu) but I get the same errors.
How can I fix this problem with the division operation?
*******************
Is my formulation of the objective function OK in how I sum only for storeB or do I have to use such_that or any other type of control?
How do I display the objective function?
*******************
What are these numbers in the output?
constraints
0 -1.79769e+308 0 0 -0
1 -1.79769e+308 0 0 -0
2 -1.79769e+308 0 0 -0
3 -1.79769e+308 0 0 -0
My four constraints are supposed to have only three terms (two on the left and one on the right)
********************
What is this?
Objective
-1 0 0
-1 1 -0
-1 2 -0
********************
If it helps at all: the model is a simple DEA formulation (primal).
I understand some of my questions may be more C++ than flopcpp questions but I can't tell.
I will appreciate help on any of these questions and on any other comments you may have on the model formulation.
Thanks in advance.
Mario
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