<div dir="ltr"><div><div><div><div><div><div>Hi Gerald,<br><br></div>Thank you very much for your response. I let SCIP delete variables by setting the two flags (pricing/delvars and pricing/delvarsroot) and marking each variable that I add as deletable. But it does not seem to help reduce the memory usage. <br>
<br></div>I usually run my code with a 24 hour limit. For one of the test-cases, it started running out of memory after around 10 hours. <br></div>In this duration, the number of variables inserted by the pricer was around 10^6. I am not sure if any of them got deleted. On my system, the optimization job was killed by the OS when memory usage reached around 32G. <br>
<br>In order to terminate more gracefully and atleast report the current results, I added a small feature at the end of each pricing round: I computed the current memory usage using some system calls and if it exceeded 25G, I set the SCIP solver time limit to the current clock time. I have attached a log file with all the statistics reported by SCIP for the optimization. <br>
<br></div>Another thing I noticed was that the memory usage typically peaks during the LP relaxation solving step. Is this typical ?<br></div>Based on the log file, do you have any suggestions for any optimization parameters I could tweak to reduce the memory usage ?<br>
</div><div><br></div><div>Thanks,<br><br>Abde Ali <br></div><div class="gmail_extra"><br><br><div class="gmail_quote">On Tue, Jul 22, 2014 at 5:44 AM, Gerald Gamrath <span dir="ltr"><<a href="mailto:gamrath@zib.de" target="_blank">gamrath@zib.de</a>></span> wrote:<br>
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Dear Abde Ali,<br>
<br>
you could try to let SCIP delete variables which are (probably) not
needed anymore. Please have a look at the FAQ:<br>
<a href="http://scip.zib.de/doc/html/FAQ.php#howtodeletevariables" target="_blank">http://scip.zib.de/doc/html/FAQ.php#howtodeletevariables</a><br>
<br>
How many variables do you generate? And how much memory do you have
available, how long does it take until you run out of memory?<br>
<br>
Best,<br>
Gerald<br>
<br>
<div>Am 14.07.2014 13:42, schrieb Abde Ali
Kagalwalla:<br>
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<div>Dear SCIP developers,<br>
<br>
</div>
Firstly, I would like to thank you for all your help in
working with the SCIP optimization framework. Using
SCIP, we recently had a paper titled "Benchmarking of
Mask Fracturing Heuristics" accepted at the
International Conference on Computer-Aided Design
(ICCAD) 2014. <br>
<br>
</div>
In our project, we are solving very large ILPs using
branch-and-price. We run the optimizer with a fixed time
limit and report the best lower and upper bound. This
works reasonably well for most of our testcases. But there
are some testcases, where the total number of columns
added by the pricer (over several iterations) keeps
increasing and eventually the program uses too much memory
and is killed by the OS. <br>
<br>
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Now my question is if there is a way to avoid this. Is it
possible to specify some limit on the number of active
variables, etc. that could help us avoid this problem ?<br>
<br>
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Regards,<br>
<br>
</div>
Abde Ali <br>
</div>
<br>
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