[SCIP] Does SCIP implement user cuts?

[Alex Meiburg]

User cuts are controlled more precisely in SCIP than in some other systems.
When calling `SCIPcreateConsLinear` to add an LP constraint, there are a
number of flags that can be set, that regulate the behavior of SCIP, and
make it act like a necessary constraint, a user cut, a lazy constraint, or
a so-called "optimality constraint". You can glance at the extended list of
arguments here:
https://scipopt.org/doc/html/cons__linear_8c_source.php#l17832 The flags
range from "initial" to "stickingatnode".

The simpler function, `SCIPcreateConsBasicLinear`, you can see at
https://scipopt.org/doc/html/cons__linear_8c_source.php#l18021 -- and it
provides default values for all those flags, as {TRUE, TRUE, TRUE, TRUE,
TRUE, FALSE, FALSE, FALSE, FALSE, FALSE}.

For adding user cuts, the recommended approach is to change `initial` to
false, `enforce` and `check` to false, and `removable' to true, so that it
looks like {FALSE, TRUE, FALSE, FALSE, TRUE, FALSE, FALSE, FALSE, TRUE,
FALSE}. These are how the flags are set in reader_lp.c, at least:
https://scipopt.org/doc/html/reader__lp_8c_source.php#l01773

The documentation can explain exactly what flipping those four flags does,
better than I can. :) You should definitely set the `check` to false and
`removable` to true, but I think `initial` and `enforce` could each go
either way -- you might want to try it both ways and see which gives you
better performance.

Best,
Alex
_______________________________
Alexander Meiburg, PhD
University of California, Santa Barbara


On Thu, Jul 20, 2023 at 5:23 AM Lastra Diaz Jose <j.lastra at lectra.com>
wrote:

> Dear all,
>
>
>
> I wonder if SCIP implements valid user cuts. They are valid inequalities
> which the user inserts into the model before solving it, and the solver
> decides when and how use them to cut off LP solutions.
>
>
>
> Regards,
>
> Juan
>
>
>
> [image: cid:image001.png at 01D4B3E6.540B6570]
>
> *Juan J. Lastra Díaz, PhD*
>
> *Advanced Research department*
>
>
>
> *t **:   *+34 917 88 88 65
>
> *e** :   *j.lastra at lectra.com
>
> [image: cid:image002.png at 01D4B3E6.540B6570]
> <https://www.linkedin.com/company/8538/>[image:
> cid:image003.png at 01D4B3E6.540B6570]
> <https://www.facebook.com/LectraOfficial/>[image:
> cid:image004.png at 01D4B3E6.540B6570]
> <https://www.instagram.com/lectraofficial/>[image:
> cid:image005.png at 01D4B3E6.540B6570]
> <https://www.youtube.com/user/LectraTechChannel?hl=fr>[image:
> cid:image006.png at 01D4B3E6.540B6570] <https://blog.lectra.com/>
>
> C/ Vía de los Poblados, 1 - Edif. C, 1ª Plta.
>
> P.E. Alvento - 28033 Madrid - España
>
> *lectra.com* <http://www.lectra.com/>
>
>
>
> This e-mail and any attached files may contain confidential information
> which is intended exclusively for the recipient. If you are not the
> specified recipient, you should delete this e-mail from your system
> immediately, and inform the sender without delay. Reading, distributing,
> copying, or any other unauthorized use of this e-mail and its attached
> files is strictly forbidden. Thank you for your comprehension.
>
>
>
> Este correo electrónico y cualquier archivo adjunto pueden contener
> información confidencial que está destinada exclusivamente al destinatario.
> Si usted no es el destinatario especificado, debe eliminar este correo
> electrónico de su sistema inmediatamente e informar al remitente sin
> demora. Está terminantemente prohibido leer, distribuir, copiar o cualquier
> otro uso no autorizado de este correo electrónico y sus archivos adjuntos.
> Gracias por su comprensión.
>
>
> _______________________________________________
> Scip mailing list
> Scip at zib.de
> https://listserv.zib.de/mailman/listinfo/scip
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://listserv.zib.de/pipermail/scip/attachments/20230720/b2bcb051/attachment.html>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image001.png
Type: image/png
Size: 6491 bytes
Desc: not available
URL: <http://listserv.zib.de/pipermail/scip/attachments/20230720/b2bcb051/attachment.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image002.png
Type: image/png
Size: 2149 bytes
Desc: not available
URL: <http://listserv.zib.de/pipermail/scip/attachments/20230720/b2bcb051/attachment-0001.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image003.png
Type: image/png
Size: 2033 bytes
Desc: not available
URL: <http://listserv.zib.de/pipermail/scip/attachments/20230720/b2bcb051/attachment-0002.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image004.png
Type: image/png
Size: 2340 bytes
Desc: not available
URL: <http://listserv.zib.de/pipermail/scip/attachments/20230720/b2bcb051/attachment-0003.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image005.png
Type: image/png
Size: 2117 bytes
Desc: not available
URL: <http://listserv.zib.de/pipermail/scip/attachments/20230720/b2bcb051/attachment-0004.png>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: image006.png
Type: image/png
Size: 2115 bytes
Desc: not available
URL: <http://listserv.zib.de/pipermail/scip/attachments/20230720/b2bcb051/attachment-0005.png>