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## [Help-glpk] Subject to two conditions

**From**: |
João Vilela |

**Subject**: |
[Help-glpk] Subject to two conditions |

**Date**: |
Wed, 10 Nov 2010 14:18:59 +0000 |

**User-agent**: |
Mozilla/5.0 (X11; U; Linux i686; pt-PT; rv:1.9.2.12) Gecko/20101027 Thunderbird/3.1.6 |

Dear all,
I'm solving a variation of a max flow problem in a graph, where:
set V, default {1..n}; /* is a set of nodes */
set E, within V cross V; /* is a set of arcs */
set L, within E cross E; /* is a set to map edges to edges */

`var x2{(i,j) in E}, binary; /* x2[i,j] indicates whether there is any
``flow going through link (i,j) */
`
And I have the following condition:

`> s.t. condition{(i,j) in E}: (sum{(i,j,i1,j1) in L} x2[i1,j1] <=0) or
``(sum{(i,j,i1,j1) in L} x2[i1,j1] >= 2);
`

`Basically, this means that I need the sum of those x2[i1,j1] to be
``different from 1 (i.e. less or equal to 0 *or* bigger or equal than 2).
``Although, this code gives me the following error:
`
"operand preceding <= has invalid type"
Any idea?
Thank you,
Joao

**[Help-glpk] Subject to two conditions**,
*João Vilela* **<=**