[Scip] Scope for improving performance?

[Vivek Periaraj]

Hi Tobias,

Setting CPX_PARAM_PRRIND to steepest pricing more or less gives me the same time. I have also set CPX_PARAM_ADVIND to 0 in my runs. Since I keep resolving the same problem, this could have impact. If so, is there a SCIP param that could turn off ADVIND, then I could test with that. I don't know how to set a CPLEX param through SCIP.

Regards,
Vivek.

----- Original Message ----- 

From: "Tobias Achterberg" <achterberg at zib.de> 
To: "Vivek Periaraj" <vivek.periaraj at gmail.com> 
Cc: scip at zib.de, "Mojtaba Maghrebi" <maghrebi at unsw.edu.au> 
Sent: Thursday, April 18, 2013 5:56:48 PM 
Subject: Re: [Scip] Scope for improving performance? 

Hi Vivek, 

one reason could be the pricing rule that SCIP uses for the CPLEX LP 
solves. To verify this, I would do your CPLEX-standalone tests again, 
using different pricing rules to assess their impact. I think that SCIP 
is using steepest edge pricing. 

Tobias 


On 04/18/13 12:39, Vivek Periaraj wrote: 
> Hi SCIP, 
> 
> For a model I have, each iteration in SCIP currently takes about 45 seconds average to resolve the LP with added/priced columns. I use CPLEX as the LP solver. If I do the adding of columns and resolving in CPLEX alone, it takes about 13 seconds average. (I did this for testing purposes). I have currently not included any of the heuristics, propagators and separators. Is the extra time (32 seconds) spent in creating a new CPLEX object for every resolve and if so, is there any way to improve performance here? If I use any other LP solver, can I improve performance? If SCIP is doing something additional, does the extra time of 32 seconds make sense? The problem size at the beginning of the root node is 6076 cols and 8000 rows. 
> 
> Regards, 
> Vivek. 
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