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--></style></head><body lang="FI" link="#0563C1" vlink="#954F72"><div class="WordSection1"><p class="MsoNormal"><a name="_Hlk17275022"><span lang="EN-US">Hello,</span></a></p><p class="MsoNormal"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US">I have one very simple example problem in lp format. I get two different optimization results from different solvers.</span></span></p><p class="MsoNormal"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US">CBC and Cplex give same result which is actually not optimal. More optimal result is achieved using SCIP. Also CBC gives same result using AMPL model.</span></span></p><p class="MsoNormal"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US">Lp model needed to be modified a little for CBC due to quadrative constraints. Models attached.</span></span></p><p class="MsoNormal"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US">One strange thing with CBC (and Cplex) is, that objective value is not correct. Correct delta_squares value calculated from the optimization result is </span></span><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US" style="color:black">112350.85 and the reported value is 107553.69.</span></span></p><p class="MsoNormal"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US" style="color:black">SCIP and CBC with AMPL give objective value 110442.85, which is more optimal than the result above.</span></span></p><p class="MsoNormal"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US" style="color:black">SCIP (and CBC with AMPL) result:</span></span></p><p class="MsoPlainText"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US">x$30 8 (obj:0)</span></span></p><p class="MsoPlainText"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US">x$50 1 (obj:0)</span></span></p><p class="MsoPlainText"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US">x$60 11 (obj:0)</span></span></p><p class="MsoPlainText"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US">delta_squares 110442.85 (obj:1)</span></span></p><p class="MsoNormal"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US" style="color:black"> </span></span></p><p class="MsoNormal"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US" style="color:black">CBC (and Cplex) result:</span></span></p><p class="MsoPlainText"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US">delta_squares 107078.000000</span></span></p><p class="MsoPlainText"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US">x$60 13.000000</span></span></p><p class="MsoPlainText"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US">x$40 2.000000</span></span></p><p class="MsoPlainText"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US">x$30 5.000000</span></span></p><p class="MsoNormal"><span style="mso-bookmark:_Hlk17275022"><span lang="EN-US" style="color:black">and the real objective value is 112350.85</span></span></p><span style="mso-bookmark:_Hlk17275022"></span><p class="MsoNormal"><span lang="EN-US" style="color:black">Any idea what is going on?</span></p><p class="MsoNormal"><span lang="EN-US" style="color:black">BR, Juhani</span></p><p class="MsoNormal"> </p></div></body></html>