<div dir="ltr"><div class="gmail_default" style="font-family:monospace,monospace;font-size:small">Hi,</div><div class="gmail_default" style="font-family:monospace,monospace;font-size:small"><br></div><div class="gmail_default" style="font-family:monospace,monospace;font-size:small">AFAIK, now there are two Gomory cut generators available in CBC (Cgl): CglGomory and CglGMI. Does this overflow affects both versions ? </div><div class="gmail_default" style="font-family:monospace,monospace;font-size:small">Which version is recommended for general use now ? Should we do some tests to determine that ?</div><div class="gmail_default" style="font-family:monospace,monospace;font-size:small"><br></div><div class="gmail_default" style="font-family:monospace,monospace;font-size:small"><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">2017-05-16 15:44 GMT-03:00 John Forrest <span dir="ltr"><<a href="mailto:john.forrest@fastercoin.com" target="_blank">john.forrest@fastercoin.com</a>></span>:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
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<div class="m_-1514774175081633051moz-cite-prefix">Modified in trunk (can be copied to
stable). Just for now I have left it as was unless GOMORY_LONG is
defined in configure. If anyone is interested they could see what
difference it makes (on my first test it was slower - but then
invalid cuts can be very powerful!). There may be some connection
with queries about accuracy of Gomory cuts in 2015
(GOMORY_RELAX_NUMBER).<span class=""><br>
<br>
John Forrest <br>
<br>
<br>
On 16/05/17 10:47, Tobias Stengel wrote:<br>
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<p class="MsoNormal">Hi,<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">I noticed an integer overflow in
CglGomory.cpp / nearestRational(double, int) lines 445 and
446. That specific MIP is solved correctly, but I have no idea
whether such an overflow can lead to wrong cuts that e.g. cut
off the optimal solution. Anyway integer overflow is undefined
behaviour in C/C++ and the returned fractional is not „near“
the input…<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">2 parameter sets for nearestRational that
lead to overflow can be found in the attached test program.
Does anyone know how nearestRational works and how the
overflow can be fixed properly?<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Thanks<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal">Tobias<u></u><u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
<p class="MsoNormal"><u></u> <u></u></p>
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<br></blockquote></div><br><br clear="all"><div><br></div>-- <br><div class="gmail_signature" data-smartmail="gmail_signature"><div dir="ltr"><div><span style="font-family:monospace,monospace">=============================================================<br>Haroldo Gambini Santos<br>Computing Department<br>Universidade Federal de Ouro Preto - UFOP<br>email: haroldo [at ] <a href="http://iceb.ufop.br" target="_blank">iceb.ufop.br</a><br>home/research page: <a href="http://www.decom.ufop.br/haroldo/" target="_blank">www.decom.ufop.br/haroldo</a><br><br><br>It has long been an axiom of mine that the little things are infinitely<br>the most important.<br> -- Sir Arthur Conan Doyle, "A Case of Identity"<br></span></div></div></div>
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