# Huge difference between the solution with gap and without gap - quadratic objective function

 0 I have a model with quadratic objective function and linear constraints. I am using CPLEX to solve a minimization problem. I have set the gap value %0.0 and I have noticed that the model loses a lot o time around very low gap values and I have noted the objective function value at low gap values. When I set the gap those low values, I have obtained an objective function value which is much more higher than the one I have noted, and this value cannot be true according to the gap. What can be the reason? Is there any setting for quadratic programming which I might have missed? Thank you in advance. asked 17 Apr '15, 16:14 yasemin 11●1●3 accept rate: 0% 1 Is this a continuous QP or a mixed integer QP? Assuming it's mixed integer, it might help if you showed the last several lines of the node log. (17 Apr '15, 19:53) Paul Rubin ♦♦ It is a mixed integer QP. Here are some lines and last lines of the node log at gap %0.0:  Nodes Cuts/ Node Left Objective IInf Best Integer Best Bound ItCnt Gap 7130 450 cutoff 72249.0000 72240.2000 103954 0.01% * 8930+ 469 72247.0000 72240.2000 133305 0.01% * 9527+ 458 72243.0000 72240.2000 141544 0.00% 2685010 21898 72241.0000 10 72243.0000 72241.0000 36477426 0.00% 2793907 19769 72241.0000 9 72243.0000 72241.0000 37725151 0.00% 2905181 10260 72242.0000 18 72243.0000 72242.0000 38864248 0.00%  Last lines when the gap is 0.01%:  Nodes Cuts/ Node Left Objective IInf Best Integer Best Bound ItCnt Gap 521813 13800 cutoff 81683.0000 81664.2000 4607042 0.02% 542708 12295 cutoff 81683.0000 81664.4531 4803536 0.02% 563565 6666 cutoff 81683.0000 81666.3333 4966647 0.02%  I know the optimal objective function value is 72243, but the model with gap updates best bound in a way that I couldn't understand and finds incorrectly high z*. (18 Apr '15, 04:02) yasemin

 toggle preview community wiki

By Email:

Markdown Basics

• *italic* or _italic_
• **bold** or __bold__
• image?![alt text](/path/img.jpg "Title")
• numbered list: 1. Foo 2. Bar
• to add a line break simply add two spaces to where you would like the new line to be.
• basic HTML tags are also supported

Tags:

×191
×5
×3
×1