[SCIP] Accessing the rows added by the constraint handler in the pricer

Mon Jul 27 22:13:46 CEST 2020

James Cussens had also written me and I am attaching his email here.

Hi Naga,

I've been doing similar things to you and had similar problems. What fixed it for me was:

1. Making sure the row was marked as modifiable in the call to  SCIPcreateEmptyRowConshdlr
2. Not releasing the row

I got complaints about adding modifiable rows to the cut pool, so I just stopped doing that.

I assume that rather than modifying an existing row one could delete the existing row and create a new one to end up in the same place. My assumption is that modifying existing rows is more efficient but I have not actually checked this.

James

On Mon, 27 Jul 2020 at 10:47, Naga Venkata Chaitanya Gudapati - nagavenkata.gudapati at studio.unibo.it <nagavenkata.gudapati at studio.unibo.it> wrote:
Hello SCIP community,

I add a few rows using a  constraint handler and the SCIPaddRow() function in the said constraint handler. I only add rows at the root node and I collect all these rows in an std::vector which I then pass on to the pricer. Whenever I add a new variable, I have to check the rows added by the constraint handler too and add the new variable to those rows if certain conditions are met. But I am getting an error here:

[lp.c:2053] ERROR: cannot add a coefficient to the locked unmodifiable row <row_3_OR_1>
[lp.c:5543] ERROR: Error <-9> in function call
[var.c:14086] ERROR: Error <-9> in function call
[scip_lp.c:1650] ERROR: Error <-9> in function call
[pricer_problem.cpp:437] ERROR: Error <-9> in function call

I am not sure if it is possible to add variables to the generated rows in the pricer.  Could someone let me know what the issue is here?

Thanks a lot for the help,
Nag
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--
James Cussens
Room CSE/239
Dept of Computer Science
University of York
York YO10 5GE, UK
Tel    +44 (0)1904 325371
http://www.cs.york.ac.uk/~jc
http://www.york.ac.uk/docs/disclaimer/email.htm

________________________________________
From: Scip <scip-bounces at zib.de> on behalf of Naga Venkata Chaitanya Gudapati - nagavenkata.gudapati at studio.unibo.it <nagavenkata.gudapati at studio.unibo.it>
Sent: Monday, July 27, 2020 12:36 PM
To: scip at zib.de
Subject: Re: [SCIP] Accessing the rows added by the constraint handler in       the     pricer

I think I figured out the problem. I should have it modifiable in the creation of the row.

________________________________________
From: Scip <scip-bounces at zib.de> on behalf of Naga Venkata Chaitanya Gudapati - nagavenkata.gudapati at studio.unibo.it <nagavenkata.gudapati at studio.unibo.it>
Sent: Monday, July 27, 2020 11:44 AM
To: scip at zib.de
Subject: [SCIP] Accessing the rows added by the constraint handler in the       pricer

Hello SCIP community,

I add a few rows using a  constraint handler and the SCIPaddRow() function in the said constraint handler. I only add rows at the root node and I collect all these rows in an std::vector which I then pass on to the pricer. Whenever I add a new variable, I have to check the rows added by the constraint handler too and add the new variable to those rows if certain conditions are met. But I am getting an error here:

[lp.c:2053] ERROR: cannot add a coefficient to the locked unmodifiable row <row_3_OR_1>
[lp.c:5543] ERROR: Error <-9> in function call
[var.c:14086] ERROR: Error <-9> in function call
[scip_lp.c:1650] ERROR: Error <-9> in function call
[pricer_problem.cpp:437] ERROR: Error <-9> in function call

I am not sure if it is possible to add variables to the generated rows in the pricer.  Could someone let me know what the issue is here?

Thanks a lot for the help,
Nag
_______________________________________________
Scip mailing list
Scip at zib.de
https://listserv.zib.de/mailman/listinfo/scip

_______________________________________________
Scip mailing list
Scip at zib.de
https://listserv.zib.de/mailman/listinfo/scip