[Top][All Lists]

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
## Re: [Help-glpk] operand preceding == has invalid type

**From**: |
Andrew Makhorin |

**Subject**: |
Re: [Help-glpk] operand preceding == has invalid type |

**Date**: |
Thu, 14 Oct 2010 23:11:37 +0400 |

>* I am new to linear programming and I am having difficulty formulating the*
>* objective function. glpsol is able to find a solution with a null (0)*
>* objective function, but cannot process this objective function:*
>* *
>* minimize objective_function:*
>* sum{(i11,j11,k11,i12,j12,k12) in LogicalLink,*
>* (i21,j21) in PhysicalSwitch, k21 in 1..24,*
>* (i22,j22) in PhysicalSwitch, k22 in 1..24:*
>* x[i12,j12,k12,i22,j22,k22] + x[i11,j11,k11,i21,j21,k21] == 2}*
>* sqrt(*
>* (x_offset[i21,j21,k21] - x_offset[i22,j22,k22])**2 +*
>* (y_offset[i21,j21,k21] - y_offset[i22,j22,k22])**2*
>* );*
>* *
>* I'm trying to map a logical network onto a physical network. Logical*
>* switches with M ports are mapped to physical switches with N ports (N >= M).*
>* A logical switch port is mapped to a physical switch port. The constraints*
>* by themselves give a feasible solution, but I wanted to add an optimization*
>* function to minimize the total length of physical cable. I'm attaching to*
>* complete MathProg program below.*
Glpk is intended for lp/mip only and therefore does not allow quadratic
objectives like in your instance. You can approximate your objective by
a piecewise linear function using a standard technique; since your
objective is convex, no binary variables are needed. Another way is to
use a quadratic programming package.

[Prev in Thread] |
**Current Thread** |
[Next in Thread] |

**Re: [Help-glpk] operand preceding == has invalid type**,
*Andrew Makhorin* **<=**