Combining eplex solver with repair solver

From: Simone Riccucci <>
Date: Mon 10 Oct 2005 02:23:35 PM GMT
Message-ID: <>
Hi everybody,

I'm a newby of Eclipse and I'm trying to solve some simple exercizes 
using the eplex solver in combination with repair solver.

My problem is as follow:
(1) Scheduule Repair

Name Preferred Start Time Duration
a 1 2
b 3 2
c 4 5
d 6 2
e 7 6
f 9 2
g 10 2

These tasks must all be executed on one machine – they cannot overlap in 

(a) Use a linear solver model to minimise the sum of the differences 
between the task start times and their preferred start times. Ignore the 
resource constraints, so the first solution will simply choose the 
preferred times.

(b) Use the repair solver to detect overlapping tasks in the solution 
found by the linear solver, and add a new linear constraint which 
prevents them from overlapping. Post an alternative constraint on 
backtracking. Specify a heuristic to choose which conflict to fix next.

(c) Combine these solvers to solve the problem.

I had no problem with point (a) but I have no idea how to combine the 
eplex with repair solver. In the tutorial there is an example for 
combining ic and repair solver. But no example for "probing" with eplex 

I post a piece of code I made until now:

% Search solution by tentative assignement %
repair_conflicts(StartTimes) :-
( List = [] -> set_to_tent(StartTimes) ;
%Choose next constraint to fix according to an heuristic
% I can not retrieve the duration I have to use some kind of structure.
% This predicate bind the value to S1 and S2 according to some criteria
% Maybe do I have to post constraint here with call(constraint) predicate?

% Defines the set of constraints preventing the tasks overlapping %
% and construct the repair set %
no_overlap(StartTimes,Duration,BooleanVar) :-
(for(I,1,L), foreach(S1,StartTimes),foreach(D1,Duration),
param(StartTimes), param(L), param(Duration),param(BooleanVar) do
param(S1), param(D1), param(I), param(BooleanVar) do
(I=\=J -> B1 is BooleanVar[1,I,J], B2 is BooleanVar[2,I,J],
S1+100 - B1*100 $>= S2+D2 r_conflict cs,
S2+100 - B2*100 $>= S1+D1 r_conflict cs,
B1+B2 $>= 1 r_conflict cs;true)

My main problem is in the procedure repair_conflicts where I have to 
enforce the constraint to eplex and use the results in some way.

Thank you very much to anyone that can help me.

Simone Riccucci


Simone Riccucci - PhD Student in Computer Science
Dep. of Computer Science - University of Bologna
via Mura Anteo Zamboni, 7 - 40127 Bologna (Italy)
Received on Mon Oct 10 15:27:24 2005

This archive was generated by hypermail 2.1.8 : Wed 16 Nov 2005 06:07:39 PM GMT GMT