[SCIP] Creating a new Branching Rule in SCIP

[Leon Eifler]

Hi once again Matheus,

you can see the priorities in each of the 'branch_*.c' files. I quickly 
grepped them all for you:

./scip/branch_inference.c:47:#define BRANCHRULE_PRIORITY 1000
./scip/branch_nodereopt.c:34:#define BRANCHRULE_PRIORITY -9000000
./scip/branch_random.c:43:#define BRANCHRULE_PRIORITY      -100000
./scip/branch_vanillafullstrong.c:48:#define BRANCHRULE_PRIORITY        
-2000
./scip/branch_cloud.c:59:#define BRANCHRULE_PRIORITY        0
./scip/branch_xyz.c:31:#define BRANCHRULE_PRIORITY        0
./scip/branch_multaggr.c:61:#define BRANCHRULE_PRIORITY        0
./scip/branch_allfullstrong.c:62:#define BRANCHRULE_PRIORITY -1000
./scip/branch_leastinf.c:37:#define BRANCHRULE_PRIORITY      50
./scip/branch_mostinf.c:37:#define BRANCHRULE_PRIORITY      100
./scip/branch_pscost.c:46:#define BRANCHRULE_PRIORITY      2000
./scip/branch_fullstrong.c:48:#define BRANCHRULE_PRIORITY      0
./scip/branch_relpscost.c:60:#define BRANCHRULE_PRIORITY 10000
./scip/branch_lookahead.c:78:#define BRANCHRULE_PRIORITY        0
./scip/branch_distribution.c:83:#define BRANCHRULE_PRIORITY 0

So you can see that reliability pseudocost branching 
(branch_relpscost.c) has the highest priority of 10000.

To also answer the previous question: You can get local variable bounds 
by calling "SCIPvarGetLbLocal" and "SCIPvarGetUbLocal", respectively. 
There is also a page in the documentation that might help you in finding 
C-API methods easier on your own: https://scip.zib.de/doc-7.0.0/html/DOC.php

Best,
Leon

On 27.05.20 23:48, Matheus Ota wrote:
> Hi,
>
> I think I implemented correctly a branching rule that inherits from 
> ObjBranchRule, but I don't know what value I should assign for the 
> priority. I tried 1000 and it was not being called, I tried 100000 and 
> it was called ok. Just to be sure, where can I find the priority 
> values of the other branching rules used by SCIP?
>
> Thanks,
> Matheus
>
> Em ter., 26 de mai. de 2020 às 12:24, Matheus Ota 
> <matheusota at gmail.com <mailto:matheusota at gmail.com>> escreveu:
>
>     Hi Leon,
>
>     Thanks for your detailed answer! Yes, I want to query if the lower
>     bound of the variable equals the upper bound, and what is this value.
>
>     Thanks again,
>     Matheus
>
>     Em ter., 26 de mai. de 2020 às 04:57, Leon Eifler <eifler at zib.de
>     <mailto:eifler at zib.de>> escreveu:
>
>         Hello Matheus,
>
>         everything you want to achieve can be implemented in a
>         branching rule. I
>         don't think there is a benefit of doing this in a constraint
>         handler. In
>         your branching rule you can create to child nodes and add all
>         bound
>         changes that you want to do for S and T to those child nodes.
>
>         > Also, in order to select the sets S and T I also need to
>         know all the
>         > variables already fixed to 0 and to 1. Is there any way of
>         doing this?
>         > Should I store all the variables fixed in each branching in
>         a data
>         > structure? Or there is an easier way of just checking if the
>         variable
>         > is already fixed or not?
>
>         You can get all fractional variables by calling
>         SCIPgetLPBranchCands (or
>         do you think of fixed as in local lower bound equals local
>         upper bound?)
>
>         > Also, my idea for branching is not enough to separate all
>         fractional
>         > solutions. So when it is not possible to use my branching, I
>         want SCIP
>         > to use the branching it normally uses (I guess it is strong
>         > branching). Could anyone that knows about this give me some
>         help here?
>
>         You do not have to do anything here. If you give your
>         branching rule a
>         high priority it will get called first. Just ensure that your
>         branching
>         rule sets the result pointer to SCIP_DIDNOTFIND or SCIP_DIDNOTRUN
>         (whichever makes more sense) if it does not find a branching.
>         Then the
>         branching rule with the next hightest priority will get called.
>
>         Best,
>         Leon
>
>
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