[Fwd: Integer solutions]
Andrew Makhorin <[email protected]> Wed, 18 Jan 2023 19:49:24 +0300
| Newsgroups | gmane.comp.gnu.glpk |
|---|---|
| Message-ID | <[email protected]> |
--=-aBqfBZNtSkdES0o7yFlv Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8bit -------- Forwarded Message -------- Date: Tue, 17 Jan 2023 20:33:01 -0800 Subject: Integer solutions To: '[email protected]' <[email protected]> From: [email protected] > <!-- > /* Font Definitions */ > @font-face > {font-family:"Cambria Math"; > panose-1:2 4 5 3 5 4 6 3 2 4;} > @font-face > {font-family:Calibri; > panose-1:2 15 5 2 2 2 4 3 2 4;} > /* Style Definitions */ > p.MsoNormal, li.MsoNormal, div.MsoNormal > {margin:0in; > font-size:11.0pt; > font-family:"Calibri",sans-serif;} > span.EmailStyle17 > {mso-style-type:personal-compose; > font-family:"Calibri",sans-serif; > color:windowtext;} > .MsoChpDefault > {mso-style-type:export-only; > font-family:"Calibri",sans-serif;} > @page WordSection1 > {size:8.5in 11.0in; > margin:1.0in 1.0in 1.0in 1.0in;} > div.WordSection1 > {page:WordSection1;} > -->Hi, > If I call glp_simplex without specifying that any variables be > integers and then call glp_intop it looks like it at least makes the > objective function an integer. > If I specify the variable should be integers as well via > glp_set_col_kind with GLP_IV then I found the time to solve the > problem was much larger (well to be expected I guess). > What is the process I should follow if I want to perform a real > relaxation of a full integer problem and only go to integers if the > problem is not satisfiable (mostly what I use the calls for)? > I couldn’t really see this spelled out in the docs. > I use the object function to find redundant constraints and I can see > this with both real and integer objectives. Obviously doing the real > case first would be faster. Likewise I determine feasibility of a > system of inequalities with a zero objective and want to do this in > both reals and then integers. > Thanks. > Neill. > --=-aBqfBZNtSkdES0o7yFlv Content-Type: text/html; charset="utf-8" Content-Transfer-Encoding: quoted-printable <html xmlns:v=3D"urn:schemas-microsoft-com:vml" xmlns:o=3D"urn:schemas-micr= osoft-com:office:office" xmlns:w=3D"urn:schemas-microsoft-com:office:word" = xmlns:m=3D"http://schemas.microsoft.com/office/2004/12/omml" xmlns=3D"http:= //www.w3.org/TR/REC-html40"><head></head><body lang=3D"EN-US"><div>--------= Forwarded Message --------</div><div><br></div><div><b>Date</b>: Tue, 17 J= an 2023 20:33:01 -0800</div><div><b>Subject</b>: Integer solutions</div><di= v><b>To</b>: '[email protected]' <<a href=3D"mailto:%22'[email protected]= g'%22%20%[email protected]%3e">[email protected]</a>></div><div><b>Fro= m</b>: <a href=3D"mailto:[email protected]">[email protected]</a></di= v><blockquote type=3D"cite"><!-- text/html --><meta http-equiv=3D"Content-T= ype" content=3D"text/html; charset=3Dus-ascii"><meta name=3D"Generator" con= tent=3D"Microsoft Word 15 (filtered medium)"><style><!-- /* Font Definitions */ @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4;} @font-face {font-family:Calibri; panose-1:2 15 5 2 2 2 4 3 2 4;} /* Style Definitions */ p.MsoNormal, li.MsoNormal, div.MsoNormal {margin:0in; font-size:11.0pt; font-family:"Calibri",sans-serif;} span.EmailStyle17 {mso-style-type:personal-compose; font-family:"Calibri",sans-serif; color:windowtext;} .MsoChpDefault {mso-style-type:export-only; font-family:"Calibri",sans-serif;} @page WordSection1 {size:8.5in 11.0in; margin:1.0in 1.0in 1.0in 1.0in;} div.WordSection1 {page:WordSection1;} --></style><!--[if gte mso 9]><xml> <o:shapedefaults v:ext=3D"edit" spidmax=3D"1026" /> </xml><![endif]--><!--[if gte mso 9]><xml> <o:shapelayout v:ext=3D"edit"> <o:idmap v:ext=3D"edit" data=3D"1" /> </o:shapelayout></xml><![endif]--><div class=3D"WordSection1"><p class=3D"M= soNormal">Hi,<o:p></o:p></p><p class=3D"MsoNormal">If I call glp_simplex wi= thout specifying that any variables be integers and then call glp_intop it = looks like it at least makes the objective function an integer.<o:p></o:p><= /p><p class=3D"MsoNormal">If I specify the variable should be integers as w= ell via glp_set_col_kind with GLP_IV then I found the time to solve the pro= blem was much larger (well to be expected I guess).<o:p></o:p></p><p class= =3D"MsoNormal">What is the process I should follow if I want to perform a r= eal relaxation of a full integer problem and only go to integers if the pro= blem is not satisfiable (mostly what I use the calls for)?<o:p></o:p></p><p= class=3D"MsoNormal">I couldn=E2=80=99t really see this spelled out in the = docs.<o:p></o:p></p><p class=3D"MsoNormal">I use the object function to fin= d redundant constraints and I can see this with both real and integer objec= tives. Obviously doing the real case first would be faster. Likewise I dete= rmine feasibility of a system of inequalities with a zero objective and wan= t to do this in both reals and then integers.<o:p></o:p></p><p class=3D"Mso= Normal">Thanks.<o:p></o:p></p><p class=3D"MsoNormal">Neill.<o:p></o:p></p><= p class=3D"MsoNormal"><o:p> </o:p></p></div></blockquote></body></html= > --=-aBqfBZNtSkdES0o7yFlv--