[Scip] Adding rows to cutpool
Stefan Heinz
heinz at zib.de
Fri Apr 6 17:18:54 MEST 2012
Hi,
if you want to create the cuts in forehand you can do that via linear
constraints
http://scip.zib.de/doc/html/cons__linear_8h.html#aa7aed137a4130b35b168812414413481
In that case you need set the Boolean flags to the following values:
initial = FALSE
separate = TRUE
enforce = FALSE
check = FALSE
propagate = FALSE
local = FALSE
modifiable = FALSE
removable = TRUE
stickingatnode = FALSE
This ensures that the linear constraint is not put into the initial LP
but gets separated if needed. The removable flag means that the cut
(linear constraint) can be removed from the LP relaxation if it is not
needed anymore (and if it was put into the LP relaxation before).
Best Stefan
On 04/06/2012 04:57 AM, sheetal murkute wrote:
> Hello,
>
> I am working on multi-commodity network flow problem. I could solve the
> problem with capacity and flow balancing constraints in SCIP.
> I now want to add the disaggregation constraints. I was considering adding
> these constraints in a global cut pool so that
> solver will decide which constraints are violated at each node at the
> runtime, and will add only the violated constraints. For
> this, I am using SCIPaddPoolCut to add constraints in a global cutpool (as
> in CPLEX/GLPK), before the solving starts.
>
> I store the indices and coefficients of xijk and yj variables for each
> disaggregation constraint in cutind and cutval respectively.
>
> I have gone through the SCIP documentation and examples.
> I wanted to ask which will be the appropriate method for adding these cuts
> - constraint handler/ separator/ or is there any particular
> method (such as SCIPcreateConsLinear) which can be used instead of adding
> constraint handler or separator?
>
> Thank you for your help.
>
> - Sheetal
>
>
> On Tue, Apr 3, 2012 at 5:10 AM, Gerald Gamrath<gamrath at zib.de> wrote:
>
>> Dear Sheetal,
>>
>> how do you get the indices stored in cutind and why do you think that
>> taking just the variable at this position in the SCIP variable array should
>> be the variable you want to have?
>>
>> You do not need to alloc memory if SCIPgetVars(scip) just returns the
>> pointer to the internal variable array of SCIP. Please assert, that
>> scipvars[cutind[i]]<= SCIPgetNVars(scip).
>>
>> Where do you do the generation of the cuts? It seems, that you do it
>> before the solving started, which is not allowed. What you could do then is
>> to add linear constraints, for which you set the initial flag to FALSE and
>> the separate flag to TRUE, so that they are only separated, if needed. You
>> can then also set the check and propagate flags to FALSE, because the
>> constraints are additional, redundant constraints.
>>
>> Please, also have a look at the SCIP documentation (e.g.
>> http://scip.zib.de/doc/html/SEPA.html) and the examples coming with SCIP
>> (directory examples/ in the SCIP main folder), for example the TSP example,
>> which is also written in C++ and features a Subtour constraint handler that
>> also generates cuts. Furthermore the SCIP online documentation (
>> http://scip.zib.de/doc/html/index.html) provides a search feature that
>> allows you to look up the definition of methods and their parameters.
>>
>> Best,
>> Gerald
>>
>> Am 02.04.2012 19:05, schrieb sheetal murkute:
>>
>> Hi,
>>
>> I added some asserts, and noticed that the assertions (xCol != NULL) and
>> (yCol != NULL) fail.
>> The assertions (xVar != NULL) and (yVar != NULL) do not fail.
>>
>> *I tried adding variables instead of columns:*
>> *( I want to add two variables, indices are stored in cutind, and
>> coefficient values are stored in *
>> *cutval)*
>>
>> SCIP_CALL_EXC( SCIPcreateEmptyRow(scip,&newrow,
>> namebuf.str().c_str(),-SCIPinfinity(scip), 0.0, FALSE,FALSE,FALSE) );
>> SCIP_VAR** scipvars = (SCIP_VAR**) malloc( (A*K+A) * sizeof(SCIP_VAR*));
>> scipvars = SCIPgetVars(scip);
>> for(i=0;i<=1;i++){
>> SCIP_CALL_EXC( SCIPaddVarToRow(scip, newrow, scipvars[cutind[i]],
>> cutval[i]) );
>> }
>> SCIP_CALL_EXC( SCIPaddPoolCut(scip, newrow));
>>
>> *
>> *
>> *I get the error: *
>>
>> [src/scip/var.c:11655] ERROR: cannot add untransformed original variable
>> <y#351> to LP row<row_1>
>> [src/scip/scip.c:15535] ERROR: Error<-9> in function call
>> terminate called after throwing an instance of 'SCIPException'
>> what(): method cannot be called with this type of data
>>
>>
>> Instead of using "scipvars = SCIPgetVars(scip);" , I also tried using
>> '_vars' vector where I store my scip variables for later use. This also
>> gives the same error - "cannot add untransformed original variable"
>>
>>
>>
>> -Sheetal
>>
>> On Fri, Mar 30, 2012 at 10:12 PM, Stefan Vigerske<
>> stefan at math.hu-berlin.de> wrote:
>>
>>> Hi,
>>>
>>> try adding some asserts and compile in debug mode (g++ -g):
>>>
>>> SCIP_Var* xVar=_vars[cutind[0]];
>>> assert(xVar != NULL);
>>>
>>> SCIP_COL * xCol = SCIPvarGetCol(xVar);
>>> assert(xCol != NULL);
>>> SCIP_Var* yVar=_vars[cutind[1]];
>>> assert(yVar != NULL);
>>>
>>> SCIP_COL * yCol = SCIPvarGetCol(yVar);
>>> assert(yCol != NULL);
>>>
>>> SCIP_COL** cols= (SCIP_COL**) malloc( 2 * sizeof(SCIP_COL*));
>>> cols[0]=xCol;
>>> cols[1]=yCol;
>>>
>>> SCIP_CALL_EXC( SCIPcreateRow(scip,&newrow, namebuf.str().c_str(), 2,
>>> cols, cutval, -SCIPinfinity(scip), 0, FALSE,FALSE,FALSE));
>>>
>>>
>>> Columns are only available for variables that are still active in the
>>> problem, i.e., have not been fixed or aggregated. For inactive variables,
>>> you would get a NULL from SCIPvarGetCol (I guess).
>>>
>>> It may be safer to add the variables to the row instead of the columns,
>>> since this is also possible for fixed variables:
>>> SCIP_CALL_EXC( SCIPcreateEmptyRow(scip,&newrow, namebuf.str().c_str(),
>>> -SCIPinfinity(scip), 0.0, FALSE,FALSE,FALSE) );
>>> SCIP_CALL_EXC( SCIPaddVarToRow(scip, newrow, _vars[5], 1.0) );
>>> SCIP_CALL_EXC( SCIPaddVarToRow(scip, newrow, _vars[351], -10.0) );
>>>
>>>
>>> Stefan
>>>
>>> sheetal murkute wrote:
>>>
>>>> Hi,
>>>>
>>>> I tried using SCIPvarGetCol() and SCIPaddPoolCut() methods.
>>>> I am getting segmentation fault at the SCIPcreateRow() line.
>>>>
>>>> I am now adding cuts as follows:
>>>> _vars is a vector where I store my SCIP variables.
>>>> cutind[0] = 5 ; cutind[1] = 351; // indices of nonzero row variables
>>>> cutval[0] = 1; cutval[1] = -10; // coefficients of nonzero row
>>>> variables
>>>>
>>>> SCIP_ROW * newrow;
>>>>
>>>> SCIP_Var* xVar=_vars[cutind[0]];
>>>> SCIP_COL * xCol = SCIPvarGetCol(xVar);
>>>> SCIP_Var* yVar=_vars[cutind[1]];
>>>> SCIP_COL * yCol = SCIPvarGetCol(yVar);
>>>> SCIP_COL** cols= (SCIP_COL**) malloc( 2 * sizeof(SCIP_COL*));
>>>> cols[0]=xCol;
>>>> cols[1]=yCol;
>>>>
>>>> SCIP_CALL_EXC( SCIPcreateRow(scip,&newrow, namebuf.str().c_str(), 2,
>>>> cols,
>>>>
>>>> cutval, -SCIPinfinity(scip), 0, FALSE,FALSE,FALSE));
>>>> SCIP_CALL_EXC( SCIPaddPoolCut(scip, newrow));
>>>>
>>>>
>>>> Please let me know if anything is incorrect.
>>>>
>>>>
>>>> -Sheetal
>>>>
>>>> On Wed, Mar 28, 2012 at 8:51 PM, Stefan Heinz<heinz at zib.de> wrote:
>>>>
>>>> Hi,
>>>>> The creation of your cut is not correct. The SCIP_COL* array is *not* an
>>>>> array of indices. You should use the method SCIPvarGetCol()
>>>>>
>>>>> http://scip.zib.de/doc/html/**pub__var_8h.html#**
>>>>> a75111eed912d3f76ec076b787f7a0**b12<
>>>>> http://scip.zib.de/doc/html/pub__var_8h.html#a75111eed912d3f76ec076b787f7a0b12>
>>>>>
>>>>>
>>>>>
>>>>> to get for a variable to corresponding column. To add your cut into the
>>>>> cut pool of SCIP you should use the method SCIPaddPoolCut()
>>>>>
>>>>>
>>>>> http://scip.zib.de/doc/html/**scip_8h.html#**
>>>>> a14b5af5c0722ae6284b2a2d2eb0b3**d5b<
>>>>> http://scip.zib.de/doc/html/scip_8h.html#a14b5af5c0722ae6284b2a2d2eb0b3d5b>
>>>>>
>>>>>
>>>>>
>>>>> Best Stefan
>>>>>
>>>>>
>>>>>
>>>>> On 03/27/2012 06:46 PM, sheetal murkute wrote:
>>>>>
>>>>> Hello,
>>>>>> I want to add rows to cutpool.
>>>>>> For this, I have written the code mentioned below:
>>>>>>
>>>>>> cutval = (double *) malloc((3) * sizeof(double *));
>>>>>> SCIP_CUTPOOL * cutpool;
>>>>>> SCIP_ROW * newrow;
>>>>>> SCIP_COL * cutind;
>>>>>> namebuf.str("");
>>>>>> namebuf<<"row_"<<k;
>>>>>> cutind[0] = 22 ; cutind[1] = 34; ( 22 and 34 are column numbers with
>>>>>> nonzero values, there are total 2 non-zero coefficients in a row)
>>>>>>
>>>>>> SCIPcreateRow(scip,&newrow, namebuf.str().c_str(), 2,&cutind, cutval,
>>>>>>
>>>>>> -SCIPinfinity(scip), 0, FALSE,FALSE,FALSE);
>>>>>> SCIPaddRowCutpool(scip, cutpool, newrow);
>>>>>>
>>>>>> *I am getting error saying:*
>>>>>>
>>>>>> /home/sxm4946/SCIP/**ziboptsuite-2.1.1/scip-2.1.1/**
>>>>>>
>>>>>> src/scip/scip/type_lp.h:73:
>>>>>> error: forward declaration of āstruct SCIP_Colā
>>>>>> scipmcfv2.cpp:308: error: invalid use of incomplete type āstruct
>>>>>> SCIP_Colā
>>>>>>
>>>>>>
>>>>>>
>>>>>> Can you please help me with this?
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>> ______________________________**_________________
>>>>>> Scip mailing list
>>>>>> Scip at zib.de
>>>>>> http://listserv.zib.de/**mailman/listinfo/scip<
>>>>>> http://listserv.zib.de/mailman/listinfo/scip>
>>>>>>
>>>>>>
>>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> Scip mailing list
>>>> Scip at zib.de
>>>> http://listserv.zib.de/mailman/listinfo/scip
>>>>
>>>
>>
>> --
>> Thanks with Best Regards,
>> Sheetal
>>
>> :)
>>
>>
>> _______________________________________________
>> Scip mailing listScip at zib.dehttp://listserv.zib.de/mailman/listinfo/scip
>>
>>
>>
>> _______________________________________________
>> Scip mailing list
>> Scip at zib.de
>> http://listserv.zib.de/mailman/listinfo/scip
>>
>>
>
>
>
> _______________________________________________
> Scip mailing list
> Scip at zib.de
> http://listserv.zib.de/mailman/listinfo/scip
More information about the Scip
mailing list