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LarrySnyder610

 Operations Research

General discussion for or.stackexchange.com
LarrySnyder610
Jan 24, 2022 12:46
@RobertBassett I created a semidefinite-programming tag and then made sdp a synonym of it. (Thanks for the suggestion @Rob)
LarrySnyder610
Jan 22, 2022 14:55
@RobertBassett There is an sdp tag. Do you think it would be better as semidefinite-programming?
LarrySnyder610
Jan 4, 2022 17:18
@SecretAgentMan Team effort!
LarrySnyder610
Jun 13, 2021 00:36
@NikeDattani nope, no idea
LarrySnyder610
Aug 24, 2020 20:35
@Rob I don't have a list handy
LarrySnyder610
Aug 23, 2020 13:44
Anybody feel like they have the bandwidth to put a feed together?
LarrySnyder610
Aug 23, 2020 13:43
@Rob Good idea.
LarrySnyder610
Jun 2, 2020 13:59
@MichaelFeldmeier Sorry, I hit "send" before finishing my reply to your flag. I was going to say, I agree the answer is a little "soft", but then again so is the question, so it's a little hard to say it's "not an answer". Let's let the voting decide.
LarrySnyder610
Jun 1, 2020 02:52
Yes, Happy Anniversary everyone!
LarrySnyder610
May 29, 2020 02:28
@MarkL.Stone :)
LarrySnyder610
May 28, 2020 16:28
@MarkL.Stone We have unlocked that post. In the future, maybe just ask nicely? ;)
LarrySnyder610
May 20, 2020 13:12
But if you're just posting here on chat because you need to let off a little steam, that's OK too. We are all familiar with the frustration of running into modeling roadblocks! ;)
LarrySnyder610
May 20, 2020 13:11
@MatsGranvik If you post a question in which you give your partial formulation and explain what you are trying to do next, folks here can probably help.
LarrySnyder610
May 4, 2020 13:39
@user1271772 About the "cross-pollination" question, I'm really not sure about that one. I know zero about materials. I'm afraid it's not a super-common application of OR, so it might be a little harder to find OR people who know a lot about that topic? But hopefully I'm wrong...
LarrySnyder610
May 4, 2020 13:38
I agree with @NikosKazazakis's thoughts, that there were a good handful of very active people early on.
LarrySnyder610
May 4, 2020 13:37
@user1271772 I'm not sure I know the answer to that. There were some early Meta posts encouraging lots of voting, but I'm not sure whether that had much effect. The OR community had a previous Stack-Exchange-like site that closed a few years ago, so it's also possible we already sort of knew the drill, and it was part of our culture.
LarrySnyder610
May 3, 2020 02:57
@user1271772 In general, SE frowns upon "big-list" type questions -- the questions you're referring to are examples of big-list questions. There was a lot of debate about it on OR Meta when we first started, and in the end our community had a consensus that we wanted to allow such questions. Many other communities don't like them, though.
LarrySnyder610
May 3, 2020 01:41
What, specifically, is your question about the post you linked to?
LarrySnyder610
May 3, 2020 01:40
@user1271772 Congrats on making it to private beta!
LarrySnyder610
Apr 24, 2020 15:06
@LocalSolver Thanks for that. Your answer is now un-deleted.
LarrySnyder610
Apr 24, 2020 02:29
@LocalSolver Sounds good. Thanks for your understanding, and I'm looking forward to interacting with you more on the site.
LarrySnyder610
Apr 23, 2020 13:34
For what it's worth, I think your answer here is right on point and doesn't fall into any of the traps discussed above.
LarrySnyder610
Apr 23, 2020 13:33
The norms and "rules" on the StackExchange network sometimes seem arbitrary, but they have evolved over several years and tend to work pretty well.
LarrySnyder610
Apr 23, 2020 13:20
Having said all of this, I'm certainly open to the possibility that I over-reacted on this post, and I welcome feedback from others in the community to weigh in on this. I'm tagging the other mods, @EhsanK and @TheSimpliFire, to see if they have any thoughts about it.
LarrySnyder610
Apr 23, 2020 13:19
Again, I think the or.stackexchange.com/help/promotion page gives good guidance on all of these points.
LarrySnyder610
Apr 23, 2020 13:19
(1) it mentions open-source (rather than commercial) software; (2) it discusses the software in the context of providing "lessons learned" from the answerer's experience doing something similar to what the asker was asking about; (3) it discusses both pros and cons of the software linked to; and (4) it uses the software as an example to support a broader point, rather than just pointing the asker to the software.
LarrySnyder610
Apr 23, 2020 13:19
About other posts: For sure, some posts point readers to particular pieces of software. When that is done, it is usually done in a way that is not "salesy", and it is usually in response to questions that ask for information about software. To me, the post you linked to differs from your post in a couple of ways:
LarrySnyder610
Apr 23, 2020 13:19
Your point about the set/list-based approach makes sense to me, but this was not part of your answer at all. If you write an answer that says "set/list-based approaches can be useful for TSP variants; here's an example; by the way LocalSolver can do this...", that seems like it has the potential to be a much more on-topic, useful, and valid answer.
LarrySnyder610
Apr 23, 2020 13:19
However, your answer (in my opinion) didn't feel like a direct answer to the question, and moreover (in my opinion, and in the opinion of a user who flagged it), the post ran the risk of sounding like it was "selling" a product. Note that "not an answer" is one of the reasons that a post can be flagged and removed, as is "spam".
LarrySnyder610
Apr 23, 2020 13:19
@LocalSolver The goal of OR.SE is definitely to help people solve their problems. There is no requirement to give complete solutions -- especially for homework problems, as you suggested, folks here will often point people in the right direction without spelling out the details. It is also valuable, as you said, to open people's minds to new approaches.
LarrySnyder610
Apr 22, 2020 23:29
As the help page says, "demonstrate a solution rather than simply asserting the problem can be solved." I hope this helps -- feel free to reply if you disagree or want more clarification.
LarrySnyder610
Apr 22, 2020 23:29
A "safe," non-spammy answer that is still specific to your software might look something like: "Your formulation is already sufficient to solve using a commercial solver. Further modeling improvements are probably not required. For example, we implemented your model in OpenSolver (here is some code...) and tested it on some randomly generated instances with XX nodes, and found that it solved in less than XX seconds..."
LarrySnyder610
Apr 22, 2020 23:28
Based on that alone, I probably wouldn't have deleted the answer, but it probably would have received some downvotes. However, because your answer promotes a particular piece of software, it reads as somewhat "spammy" according to the norms of Stack Exchange. The OR.SE help pages address this question, but the text is the same throughout the SE network.
LarrySnyder610
Apr 22, 2020 23:28
Hi @LocalSolver! Thanks for checking in here on chat about this -- I'm glad we can discuss it in a medium that's more conducive than the post comments. Also -- thanks for joining OR.SE, and welcome! I think your perspective and insights will be valuable here. The reason I deleted your post is that it doesn't really answer the question: The question asks about how to model the problem, and your answer suggests that the OP use a particular solver.
LarrySnyder610
Apr 4, 2020 00:20
@user1271772 yes
LarrySnyder610
Apr 2, 2020 21:40
@prubin uh, I'll get back to you on that one ;)
LarrySnyder610
Apr 2, 2020 20:43
Congrats @prubin for taking over as first place in rep points, and for being the first to cross 10k! or.stackexchange.com/users?tab=Reputation&filter=all
LarrySnyder610
Mar 18, 2020 14:13
@TheSimpliFire You did too. Sorry for tuning into this conversation late.
LarrySnyder610
Feb 8, 2020 14:59
@MarkL.Stone I'm sure no one meant to give Robert a not-nice welcome. We certainly do welcome him here, and moreover his site looks awesome and I hope we can help drive some traffic his way. At the same time, let's try to work to find the right way to post about it.
LarrySnyder610
Feb 8, 2020 14:58
I agree with @TheSimpliFire's two proposals. Either seems good to me.
LarrySnyder610
Feb 8, 2020 14:01
So: I'm willing to un-delete the answer, but I think Open Opt. and the OR.SE community will be best served if we handle it a different way. What do you think?
LarrySnyder610
Feb 8, 2020 14:00
Second, his post is likely to get lost as an answer to that question -- people will only find out about his site if they happen to be reading a question about incomplete textbooks. So, I can un-delete the post, but I'm not sure that's the best course of action.
Instead, I suggest that Robert post the announcement of his site on Meta. It's not a 100% fit there either, but I think it's better there than its current location. In addition, if Open Optimization does have any incomplete textbooks by famous authors in its repository, then Robert should definitely edit his answer to point to them o…
LarrySnyder610
Feb 8, 2020 14:00
"Community" is an automated "user" so it's not as though anyone here deleted the post intentionally. Having said that, I'm not sure that the best place for Robert to post his announcement is in an answer to that question. First, it doesn't actually answer the question, which asks for incomplete textbooks by famous authors that are available on the web. Robert's post doesn't suggest any textbooks meeting those conditions.
LarrySnyder610
Feb 5, 2020 16:44
I've never run across a problem like that, but if you Google "knapsack problem negative weights" you might run across something. Or post on OR.SE!
LarrySnyder610
Feb 5, 2020 16:44
@MatsGranvik Well, if you just take the standard 0-1 knapsack problem and allow some weights to be negative, does that describe your problem? The knapsack problem already has a capacity parameter.
LarrySnyder610
Feb 5, 2020 13:29
@MatsGranvik Sorry for the slow reply. What do you mean, exactly? Are you basically saying some item "weights" would be positive and some negative?
LarrySnyder610
Jan 6, 2020 16:10
@Rob At or.stackexchange.com/help/on-topic, we do link to the MathJax page. Is this the kind of thing you mean? If not, which "help link" do you mean?
LarrySnyder610
Jan 1, 2020 14:57
@Rob We have or.meta.stackexchange.com/questions/5/… -- are you suggesting we add another MathJax help page?
LarrySnyder610
Nov 19, 2019 15:08
@SecretAgentMan OK, sounds like a plan. Thanks for raising the issue!
LarrySnyder610
Nov 18, 2019 15:22
As for the faq tag, let's see how the discussion shapes up, and if some people post answers that are more useful than mine :) we can tag it.