[Scip] Presolving Issues

[Matthias Miltenberger]

Hi Andreas,

could you send me your instance and your settings? Then I could have a 
look and maybe find out what's going wrong.

All the best
Matthias

Am 10.03.2013 14:18, schrieb Andreas Gebauer:
> Hi all,
>
> I have some issues with the presolving settings.
> The IP I'm working with has a lot of useless variables and constraints.
> Presolving deletes them in the first rounds and goes on for a while without breath-taking results.
> So I tried to set maxrounds to 10.
> It seems as if this is finished within 5 seconds but it lasts another 55 seconds until the solving process is started (I pasted the output at the bottom of the mail).
> Are there any settings I could use to avoid this behaviour?
>
> I hope, some of you guys are working on a sunday afternoon as my project deadline is tonight.
>
> Thanks a lot!
> Best regards,
> Andreas
>
> output:
> presolving:
> (round 1) 188689 del vars, 288346 del conss, 0 add conss, 208160 chg bounds, 11470 chg sides, 0 chg coeffs, 0 upgd conss, 4162 impls, 32 clqs
> (round 2) 200195 del vars, 299852 del conss, 0 add conss, 208160 chg bounds, 13453 chg sides, 0 chg coeffs, 0 upgd conss, 4162 impls, 32 clqs
> (round 3) 200756 del vars, 299853 del conss, 0 add conss, 208160 chg bounds, 13453 chg sides, 0 chg coeffs, 0 upgd conss, 4162 impls, 32 clqs
> (round 4) 200756 del vars, 300113 del conss, 0 add conss, 208514 chg bounds, 13655 chg sides, 0 chg coeffs, 0 upgd conss, 4162 impls, 32 clqs
> (round 5) 201019 del vars, 300437 del conss, 0 add conss, 208514 chg bounds, 13655 chg sides, 0 chg coeffs, 0 upgd conss, 4162 impls, 32 clqs
> (round 6) 201080 del vars, 300437 del conss, 0 add conss, 214135 chg bounds, 13655 chg sides, 0 chg coeffs, 0 upgd conss, 4162 impls, 32 clqs
> (round 7) 201103 del vars, 300437 del conss, 0 add conss, 214138 chg bounds, 13655 chg sides, 0 chg coeffs, 0 upgd conss, 4162 impls, 32 clqs
> (round 8) 201103 del vars, 300452 del conss, 0 add conss, 214138 chg bounds, 13655 chg sides, 0 chg coeffs, 0 upgd conss, 4162 impls, 32 clqs
> (round 9) 201103 del vars, 300479 del conss, 0 add conss, 214154 chg bounds, 13655 chg sides, 0 chg coeffs, 0 upgd conss, 4162 impls, 32 clqs
>     (2.9s) probing: 80/330 (24.2%) - 0 fixings, 0 aggregations, 54 implications, 0 bound changes
>     (2.9s) probing aborted: 50/50 successive totally useless probings
> (round 10) 201104 del vars, 300480 del conss, 0 add conss, 214178 chg bounds, 13655 chg sides, 0 chg coeffs, 0 upgd conss, 4252 impls, 32 clqs
>     (4.7s) probing cycle finished: starting next cycle
>     (4.8s) probing: 51/330 (15.5%) - 0 fixings, 0 aggregations, 414 implications, 0 bound changes
>     (4.8s) probing aborted: 50/50 successive totally useless probings
> presolving (11 rounds):
>   201261 deleted vars, 300619 deleted constraints, 0 added constraints, 215210 tightened bounds, 0 added holes, 13832 changed sides, 0 changed coefficients
>   4743 implications, 32 cliques
> presolved problem has 32162 variables (330 bin, 31832 int, 0 impl, 0 cont) and 15557 constraints
>       77 constraints of type <varbound>
>       32 constraints of type <setppc>
>    15412 constraints of type <linear>
>       36 constraints of type <logicor>
> transformed objective value is always integral (scale: 1)
> Presolving Time: 60.10
>
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| Matthias Miltenberger   | Zuse Institute Berlin |
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