[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
## [Help-glpk] Help using auxiliar variables

**From**: |
dhiguero |

**Subject**: |
[Help-glpk] Help using auxiliar variables |

**Date**: |
Mon, 22 Nov 2010 16:21:34 +0100 |

**User-agent**: |
RoundCube Webmail/0.4 |

Hi everybody,

` After solving the min(a,b) problem, I have found another issue with
``the formalization. I attach the code so you can test it. The current
``scenario is:
`
- A set of elements and a set of possible types.

` - Each type has an associated bandwidth so the bandwidth of each
``element must be the bandwidth of its type.
`` - Minimum and maximum thresholds for the number of elements in the
``system per type. Some elements may not be used.
`` - The objective is to minimize the number of elements used in the
``system. Right now, it is only the number of elements but in a future it
``will contain the cost associated with the work performed per element.
`

` The problem is associated with assigning bandwidth to elements. It
``seems that the solver has problems when I include equations such as:
`

`s.t. available_bandwidth_on_elements {e in Elements}: bandwidth[e] ==
``sum{t in Type} (elementType[e, t] * bandwidth_per_type[t]);
`

` If I use the equal, the solver introduces more elements than
``expected from the minimum threshold. If I change to greater or equal,
``the solver puts non-zero values in the bandwidth of unused elements.
`

` Any idea on how to model this type of assignations? The bandwidth
``variable is not part of the objective function, but I need these type
``of auxiliar variables to create future constraints in the model. Let's
``say I want to calculate the minimum number of elements such as a
``multicast message arrives on time to every element in the system and
``the total work is performed using the mimimum number of elements.
`
Regards,
Daniel

**
**`min_problem_reduced_v2.mod`

*Description:* Text document

**[Help-glpk] Help using auxiliar variables**,
*dhiguero* **<=**