[Scip] Adding rows to cutpool

Tue Apr 3 16:59:50 MEST 2012

Hi,

> 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).

Actually, this should be
  assert(cutind[i] < SCIPgetNVars(scip));

Stefan

>
> 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 <mailto: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
>> <mailto: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 a-struct SCIP_Cola-
>> scipmcfv2.cpp:308: error: invalid use of incomplete
>> type a-struct SCIP_Cola-
>>
>>
>>
>> Can you please help me with this?
>>
>>
>>
>>
>>
>>
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>>
>> --
>> Thanks with Best Regards,
>> Sheetal
>>
>> :)
>>
>>
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