[OS] Understanding linearConstraintCoefficients markups

[Horand Gassmann]

Quoting Joe <joe.boublack at gmail.com>:

>
>
> I'm trying to convert my lp_solve/LP files into OSiL file format. I
> don't understand the mapping applied on coefficients from
> linearConstraintCoefficients markups. I've found one example in the
> "OS 1.0 User's Manual" also discussed in this newsgroup. However these
> explanations is not so clear for me. I've also checked examples from
> documentations of LPFML because OSiL would be a superset of this
> language (unfortunately, markups names have been changed from LPFML to
> OSiL conventions).
>
> Maybe someone could help me to convert a small (only 4 variables, 2
> constraints, 1 objective) lp_solve/file into OSiL (the contents of
> small.lp is paste on the end of this message). Please find my attempt
> for OSiL formulation (actually, OSSolverService crashes on parsing
> this file) :

Several things: Order matters. Among the children of <instanceData>, the
<variables> element has to come first. And there is only one element named
<linearConstraintCoefficients>. It contains the entire constraint matrix,
either in row or in column format. It might be easier at first to follow the
example in row format.

#broken-small.osil ; usage : OSSolverService -osil broken-small.osil
<?xml version='1.0' encoding='UTF-8'?>
<osil xmlns='os.optimizationservices.org'>
<instanceHeader>
  <name>My broken example</name>
  <source>Manually written</source>
  <description>Any comments</description>
</instanceHeader>

<!-- Declarations -->
<variables numberOfVariables='4'>
<var name='X0' type='I'/>
<var name='X1' type='I'/>
<var name='X2' type='I'/>
<var name='X3' type='I'/>
</variables>

<!-- Objective -->
<objectives numberOfObjectives='1'>
<obj name='Example objective' maxOrMin='max'  numberOfObjCoef='1'>
  <coef idx='3'>1</coef>
</obj>
</objectives>

<!-- Constraints -->
<constraints numberOfValues='2'>
<con ub='0' lb='0'/>
<con ub='100'/>
</constraints>

<linearConstraintCoefficients numberOfValues='7'> <!-- 7 nonzeroes -->

<!-- the first row has four nonzeroes, the second three: -->

<start>
   <el>0</el>   <el>4</el>   <el>7</el>
</start>

<colIdx>
  <el>0</el>  <el>1</el>  <el>2</el>  <el>3</el>   <!-- row 0 -->
  <el>0</el>  <el>1</el>  <el>2</el>               <!-- row 1 -->
</colIdx>

<value>
  <el>-2</el>  <el>-3</el>  <el>-5</el>  <el>7</el>   <!-- row 0 -->
  <el>1</el>  <el>1</el>  <el>1</el>                  <!-- row 1 -->
</value>
</linearConstraintCoefficients>
</instanceData>
</osil>


If you want to give the <linearConstaintCoefficients> element columnwise, you
would specify:

<linearConstraintCoefficients numberOfValues='7'>

<!-- the first three columns have two nonzeroes, the last one only one: -->

<start>
   <el>0</el>   <el>2</el>     <el>4</el>   <el>6</el>   <el>7</el>
</start>

<rowIdx>
  <el>0</el>   <el>1</el>          <!-- col 0 -->
  <el>0</el>   <el>1</el>          <!-- col 1 -->
  <el>0</el>   <el>1</el>          <!-- col 2 -->
  <el>0</el>                       <!-- col 3 -->
</rowIdx>

<value>
  <el>-2</el>  <el>1</el>          <!-- col 0 -->
  <el>-3</el>  <el>1</el>          <!-- col 1 -->
  <el>-5</el>  <el>1</el>          <!-- col 2 -->
  <el>7</el>                       <!-- col 3 -->
</value>
</linearConstraintCoefficients>


HTH

gus gassmann





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