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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link="#0563C1" vlink="#954F72"><div class=WordSection1><p class=MsoNormal>Is it possible?<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I have a model that quickly comes up with a weak integer solution. I want to take that result and use it as the starting point for another solve, same columns, tighter objective.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>My expectation is that, if I have a problem that arrives at optimum after say 300 nodes, then I should be able to take the optimum solution, and feed it back into cbc with the same problem and see an immediate optimum reached. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>In efforts to achieve this demonstration, I have been working with the “prio” command. <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I have a file formatted like this:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>name,solution<o:p></o:p></p><p class=MsoNormal>E_draw(0),-100000<o:p></o:p></p><p class=MsoNormal>E_draw(1),-111112.61<o:p></o:p></p><p class=MsoNormal>E_draw(10),-109772.28<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Which I feed to cbc:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>cbc.exe c:\temp\store\lpmodel\1_292_279_2.lp -directory c:\temp\store\lpmodel\ -preprocess on -prio 1_292_279_2.values -solve -solu 1_292_279_2.val.out.solution –quit<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>with no apparent effect. Is “solution” the right column header? It seems to go straight to the linear solution ignoring the proffered solution.<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>I figured I would try the “force” command argument. With “-force 0” I get the immediate result I seek, but unfortunately:<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='margin-left:.5in'>2 fields and 3855 records<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>forceSolution was changed from -1 to 0<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>Continuous objective value is 0 - 0.35 seconds<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>Cbc0045I Solution with objective value 0 saved<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>Cbc0006I The LP relaxation is infeasible or too expensive<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>Cbc0045I Solution of 0 already found by heuristic<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>Cbc0039I On closer inspection - solution discarded<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>Cbc0039I On closer inspection - solution discarded<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>Cbc0039I On closer inspection - solution discarded<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>Cbc0021I On closer inspection node is infeasible<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:.5in'>Result - Linear relaxation infeasible<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'><o:p> </o:p></p><p class=MsoNormal style='margin-left:.5in'>Objective value: 100000000000000007629769841091887003294964970946560.00000000<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>Enumerated nodes: 0<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>Total iterations: 0<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>Time (CPU seconds): 1.06<o:p></o:p></p><p class=MsoNormal style='margin-left:.5in'>Time (Wallclock seconds): 1.06<o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal>Other values for force don’t seem to do anything. I note the solutionIn is initialized like so: <o:p></o:p></p><p class=MsoNormal><o:p> </o:p></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.5pt;font-family:Consolas;color:black'> </span><span style='font-size:9.5pt;font-family:Consolas;color:blue'>if</span><span style='font-size:9.5pt;font-family:Consolas;color:black'> (got[6] >= 0) {<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.5pt;font-family:Consolas;color:black'> solutionIn = </span><span style='font-size:9.5pt;font-family:Consolas;color:blue'>reinterpret_cast</span><span style='font-size:9.5pt;font-family:Consolas;color:black'><</span><span style='font-size:9.5pt;font-family:Consolas;color:blue'>double</span><span style='font-size:9.5pt;font-family:Consolas;color:black'> *> (malloc(numberColumns * </span><span style='font-size:9.5pt;font-family:Consolas;color:blue'>sizeof</span><span style='font-size:9.5pt;font-family:Consolas;color:black'>(</span><span style='font-size:9.5pt;font-family:Consolas;color:blue'>double</span><span style='font-size:9.5pt;font-family:Consolas;color:black'>)));<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.5pt;font-family:Consolas;color:black'> </span><span style='font-size:9.5pt;font-family:Consolas;color:blue'>for</span><span style='font-size:9.5pt;font-family:Consolas;color:black'> (iColumn = 0; iColumn < numberColumns; iColumn++)<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.5pt;font-family:Consolas;color:black'> solutionIn[iColumn] = -COIN_DBL_MAX;<o:p></o:p></span></p><p class=MsoNormal style='text-autospace:none'><span style='font-size:9.5pt;font-family:Consolas;color:black'> }<o:p></o:p></span></p><p class=MsoNormal>I expect that is by design, but if sparsely specified values are left at <span style='font-size:9.5pt;font-family:Consolas;color:black'>-COIN_DBL_MAX that would be bad?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:9.5pt;font-family:Consolas;color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:9.5pt;font-family:Consolas;color:black'>I have a bunch of SOS in the model. Do we have to turn the crank to get SOS state to match the provided column values?<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:9.5pt;font-family:Consolas;color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:9.5pt;font-family:Consolas;color:black'>Any tips or hints will be appreciated.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:9.5pt;font-family:Consolas;color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:9.5pt;font-family:Consolas;color:black'>Thanks,<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:9.5pt;font-family:Consolas;color:black'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:9.5pt;font-family:Consolas;color:black'>jkh</span><o:p></o:p></p></div></body></html>