Author: thserra

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The unsustainable lack of analytical skills for a sustainable environment

Developing an analytical model to support decision-making is a really tricky task. I did many of them in order to decide whether it was a good idea to buy an apartment or to keep renting. What differed among them was the level of detail taken into account, which progressed slowly as I learned from my previous mistakes. While most of my models pointed out that it was better to keep money on a savings account and do not lend any instead of buying an apartment for the rent that can be earned (or that I would avoid paying since I had to live somewhere), I often forgot to regard the probability that apartments would appreciate considerably in a near future. Looking back, I see that my renter did an excellent investment by renting to me and waiting for what would come. Nevertheless, that moment is gone and it does not make any sense to bet that real estate in São Paulo will keep rising in price as it did in recent years.

When it comes to a trending topic like sustainability, that is supposed to represent the concern of people with protecting the environment for future generations while exploiting it for their own survival, I have been often told of misconceptions and lost opportunities that made many initiatives on that regard produce the opposite effect. And what is worst: as conceived, sustainability is a great but sometimes overlooked application domain to leverage analytical tools.

For instance, I was told of a workplace where someone had the idea of asking for shelves above the toilet washbasins. Since the washbasins were often wet, people got used to place a paper towel below their toiletries bags. As an experiment, such shelves were placed in half of the toilets of a floor. Long after, people started to ask when those shelves would be placed in the other half, since the experiment seemed to be successful. However, they were informed that someone had to collect data to assess if less paper towels were used in the first half of the toilets or not. As many people did not bother to walk more to use the toilets with shelves, it is very likely that the person undertaking such experiment will be surprised after realizing that the use of paper towels actually increased in that half and decreased in the other half. I hope that the person manages to sum up the use on both halves to realize what happened instead of concluding that shelves increase the use of paper towels.

It is attributed to Ronald Fisher the following quote: “To consult the statistician after an experiment is finished is often merely to ask him to conduct a post mortem examination. He can perhaps say what the experiment died of.”. While it would be interesting to count with professional help, I believe that we would be better off if people working with sustainability were aware of the importance of developing analytical skills to avoid working against their own goals.

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An advanced school on handling big data for academic purposes (with full grants for Brazilian and foreign students): São Paulo Advanced School on e-Science

São Paulo state’s research council (FAPESP) is sponsoring an interesting school on e-science, which I would describe to the blog audience as analytics for academic purposes. It is said that they will offer full financial support for 25 Brazilian and 25 foreign students. The school will be held next October in the surroundings of my alma matter, Unicamp.

Further information can be found at: http://www.vision.ime.usp.br/~liu/escibioenergy/

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4 summer activities you must do before graduating + late remarks about ICAPS 2012

I recently attended to the 2012 International Conference on Automated Planning and Scheduling (ICAPS), which was held at a car distance from São Paulo (what a rare opportunity!). It was the first time that I saw something like Festivus, which featured funny debates about the relevance of the research developed by the P&S community and even a bossa nova song about three blocks that wanted to be moved. Beyond the fun and cheap transportation cost, the most remarking experiences I had there were the satellite event to gather and mentor graduate students – ICAPS Doctoral Consortium – as well as observing the differences between planners and schedulers – the former of which somewhat belonging to the OR community.

ICAPS Doctoral Consortium (DC)

DC consisted of four talks directed to PhD students and a poster presentation, during which at least two mentors were assigned to talk with each student to discuss his/her research topic.

Alan Fern managed to invite young and mid-career researchers that followed varied directions after earning their PhD and were willing to tell their stories to us.

Andrew Coles presented a talk entitle “Now what?” describing his career and how much time does it take to achieve certain positions in the academia.

Silvia Richter’s talk was mostly focused on issues such as finding motivation and realizing that it takes a lot of time to have a good idea. She also provided good figures regarding how many papers you should publish (3-4 is nice) and how much effort should you put on writing your thesis (not as much as you suppose, since only 5 people will probably read it entirely), and suggested an interesting website: 3monththesis.com.

Minh Do showed some interesting graphs to compare salaries, freedom, possibilities for changing career afterwards etc for positions like working in the industry, researching in the industry, researching in the academia and striving to be a professor with tenure. On top of that, he listed four activities that any CS undergrad student should experience to know what to do with his/her life afterwards (and that I wish I was told years ago):

  • Do a research internship in academia
  • Do an internship at the headquarters of a company
  • Work in a local startup with a good tech team
  • Work in an open source project

Scott Sanner finished the session with good tips for social networking and external presence. In the former case, he stressed the importance of talking to other researchers and getting to know more about their work (and not bragging about yours) and of giving memorable talks, or at least striving to do that. In the latter case, he talked about building a professional website and he showed his first website as a funny example of what you should not do.

I presented a poster about adaptive search methods for Constraint-Based Scheduling (CBS). The first mentor who showed up was Amanda Coles (wife of Andrew Coles, the first speaker above). We had a long and interesting talk, that let me realize how much of the theoretical background of adaptive search methods for combinatorial optimization is also valuable for planning. The second mentor was Stephen Smith, who was the advisor of a number of works related to my topic of interest. I was glad that both mentors enjoyed my research plan and gave me good advices to succeed with it.

Planning vs. Scheduling (and OR)

I have already mentioned in a former post the divide between planners and schedulers: the summer school consisted of three courses about planning and one about scheduling, the latter being easier to me than the others. While some recognize that planning methods can theoretically be used to solve scheduling problems, planners strive to be as generalist as possible when approaching a problem. Schedulers, however, prefer the opposite path and delve themselves into the structure of each problem to take the most of it. In practice, their application domains barely touch each other. Nevertheless, there are some researchers that, as we say in Brazil, are on the top of the wall that divides those areas. Even though I was feeling an outsider at some moments, there were a number of talks related to OR and a few others discussing the limits of application of each type of technique. Thus, tying together planners and schedulers seems to be a good long-term strategy to both areas.

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First impressions about ICAPS – or “How much I do not know”

ICAPS 2012 is being held nearby São Paulo. The Planning and Scheduling Summer School (well, it is winter here in the Southern hemisphere right now) was really interesting, but I might say that there is much that I need to learn about planning. Up to now, I was just an operations research practitioner with a lot of interest in scheduling problems. That changed somewhat with Roman Barták’s class about solving planning problems with CP (which is a technique I enjoy a lot). Besides, planning represents a quite different way of observing the reality and solve its problems. I will try to play a little with its methods someday.

To conclude with these first impressions, the Doctoral Consortium held this morning was a valuable source of advice from young post-docs and professors. I wish I heard some of those when I was still an undergrad student. Nevertheless, many of them are still valid to plan my career.

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CFP: OR/MS Applications in the Energy Sector of Emerging Countries at 2012 INFORMS Annual Meeting

I am organizing a session on “Applications in the Energy Sector of Emerging Countries” within the invited cluster “Operations Research and Management Science in Emerging Economies” at the INFORMS Annual Meeting.

If you are interested in presenting your abstract in this section, please contact me.

The abstract submission deadline is May 15, 2012. The title must have at most 100 characters and the abstract at most 500 (about 50 words). The conference will be held on October 14-17, 2012 in Phoenix, AZ. More information can be obtained at the conference website: http://meetings2.informs.org/phoenix2012/

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It is still time to share your work at ICAPS’12 workshops, to be held nearby São Paulo!

The upcoming edition of the International Conference on Automated Planning and Scheduling (ICAPS) will be held next June in Atibaia, São Paulo. The deadlines of some workshops has been recently extended, thus allowing more people to put together on a paper what they have been doing and have not published so far. Even if you are not thinking about submitting anything, attending to such a conference can be a double score for the opportunity of visiting an unusual place in Brazil (i.e., somewhere but Rio de Janeiro and the Northeast beaches).

Maybe I am not the right person to praise about Atibaia because I’ve never been there despite invitations from friends and living less than 50 miles away. However, it seems an interesting place for activities such as paragliding due to a big rock they have there. Besides, you will be near Brazil’s largest and most cosmopolitan city (well, that is the humble opinion of many “paulistas”, but might not be shared by our neighbors from Rio). To name but a few things worth tasting or seeing here:

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Tasting more wine with dynamic programming

The INFORMS blog suggested that O.R. bloggers wrote about food. Figuring that a good meal is usually accompanied by a good wine, I’ve decided to focus on using an Operations Research technique to maximize the number of wines someone can taste at a time. I warn in advance to connoisseurs accessing this blog by chance that my knowledge about wine tasting is very short (once in a while, I resume my reading of Jancis Jobson’s book “How to Taste Wine”, but I’m closer to the first pages than to the last ones). Anyway, I hope that some of them find dynamic programming useful for their practice.

First of all, how wine should be tasted? According to a book that I just browsed during lunch time, the following rules must be followed:

  • white before red;
  • young before old;
  • light before heavy;
  • dry before sweet.

To simplify matters, I will assume that those rules are unbreakable (are they?), I will ignore that it is recommended to taste only similar wines each time, and get to the following question: under such circumstances and provided a collection of bottles, how can I maximize the number of tastings one can do at a time?

Let’s consider as an example the following wines, which this novice considered good and attempted to roughly classify in a binary way:

W1 Argentina Finca Martha 878 Malbec 2008 red, young, heavy, dry
W2 Brazil Miolo Gammay 2010 red, young, light, dry
W3 Brazil Terranova Late Harvest Moscatel 2005 white, young, heavy, sweet
W4 Brazil Terranova Shiraz 2010 white, young, light, dry
W5 Chile Casillero del Diablo Carmenère 2009 red, young, heavy, dry
W6 Portugal Dão Cabriz 2007 red, young, heavy, dry
W7 Portugal Ramos Pinto Late Bottled Red Port 2000 red, old, heavy, sweet
W8 Portugal Sandeman White Port 2005 white, young, heavy, sweet
W9 South Africa Obikwa Pinotage 2008 red, young, light, dry

Without loss of generality and for the sake of breaking ties to avoid equivalent solutions (e.g., tasting W2 before W9 or W9 before W2), we will consider that one must proceed incrementally another in the case of a tie (i.e., W2 before W9 but not W9 before W2).

Now suppose that we start with W3 because it is white and young. Soon we will realize that only two wines can remain in our list for being also heavy and sweet: W8 and W9. Hence, W3 might not be a good starting point. However, it is easy to figure that the optimal path from W3 on is to taste W8 and then W9 because the former is white and the later red. Similarly, the optimal path starting from W8 is to proceed to W9, and from W9 is to do nothing.

Beyond the wines, do you “smell” something interesting here? We have overlapping subproblems and those optimal solutions share optimal substructures with each other. That’s where Dynamic Programming (DP) fits in! Using DP, we consider optimal solutions to varied subproblems as building blocks to find optimal solutions to increasingly bigger problems. Thus, even if those subproblems arise many times, it suffices to solve each of them once.

In the current case, we could do that by finding the best option between the following subproblems: Pi = “How many wines can I taste if I start from Wi?”, for i = 1 to 9. In turn, answering to each of those questions consists of adding one to the best answer found among wines that can be tasted after that first one. For instance, we start with W1, W2, …, or W9 to find the answers P1, P2, …, and P9. Picking W1, we have that P1 = 1 + MAX(P5, P6, P7) because W1 can only be followed by P5, P6 or P7. Note that once we answered P1, we already know the answers to P5, P6 and P7, and therefore we do not need to recalculate them in the remainder of the solving process. The act of memorizing such solutions for later recover is called memoization.

Applying DP to the current case, we will find the following answer to the subproblems:

P1 P2 P3 P4 P5 P6 P7 P8 P9
4 6 3 7 3 2 1 2 5

Working backwards, we start from W4 (P4=7) to find which wine can that can be tasted after W4 and from which point on it is possible to taste 6 wines, and so on until the last one. The final answer to our problem is the sequence W4, W2, W9, W1, W5, W6, W7.

As a final remark, I would like to remember that quantity does not mean quality. Drink responsibly and remind that a tasting experience does not necessarily means getting drunk in the end: you can always spit and enjoy the rest of your day in a better shape.

Once said that, “saúde”, “cheers”, or – as my Polish friends from the Erasmus program would say – “na zdrowie”!

 

Update: Shiraz is a grape that produces red wine, not white. Anyway, it is still possible to taste 7 out of the 9 wines at once.

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Resolutions to optimize O.R. blogging

My blog is on air for almost one year. Despite having a modest audience, lots of data has been stored about its visits and it would be ironic if a blog about Operations Research and Analytics does not use such data to improve itself. Based on some data from 2011, I’d like to commit myself to give the audience more of what they expect in 2012 and share some conclusions with other bloggers interested in doing the same.

Top 5 most viewed posts (out of 26):

# 1 Drug discovery optimization: a meeting point for data mining, graph theory and operations research
(204 unique views)

Context:

  • Motivated by an INFORMS blog challenge.
  • It is something I like and worked with in the past.
  • I found a catchy title (I guess).
  • It was a family work (my mother-in-law has a ph.D. in organic chemistry).
  • Referenced by the SYSOR Reddit channel (that made a huge difference).

# 2 Revisiting operations research elements – part I: problem, model and solution
(133 unique views)

Context:

  • Motivated by crazy discussions about what a problem, a model and a solution are.
  • I read a lot before writing.
  • It was a family work [x2] (the discussions were started by my mother-in-law and Sabrina read my drafts until they were clear to someone outside the field).
  • People look for those things on Google.

# 3 How Analytics makes Operations Research the next big thing
(111 unique views)

Context:

  • Motivated by an INFORMS blog challenge [x2].
  • It has something to do with my job.
  • I found a catchy title (I guess) [x2].
  • People look for those things on Google [x2].

# 4 Optimizing Public Policies for Urban Planning
(84 unique views)

Context:

  • Motivated by an INFORMS blog challenge [x3].
  • It is something I like and worked with in the past [x2].
  • It was a family work [x3] (Sabrina has a degree in urban planning).
  • People look for those things on Google [x3].

# 5 When the Network becomes Social: Small World Graphs and O.R.
(67 unique views)

Context:

  • Motivated by an INFORMS blog challenge [x4].
  • I read a lot before writing [x2].
  • I found a catchy title (I guess) [x3].

Lessons learned:

  • People love creative applications of O.R.
  • Telling about what you like the most helps you writing better.
  • Listening to a person around you is worth reading a dozen of papers.
  • You can learn a lot by studying further the topic you want to post about.
  • It is important to focus on being direct, concise and provide resources to those interested in more.
  • Participating on INFORMS blog challenges is a win-win strategy.

Resolutions for 2012:

  • Write more posts like those above.
  • Use more visual resources and hands-on materials.
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Over-constrained problems, soft constraints and family holiday parties – and why some companies ask for O.R. support

People are having fewer children, families are becoming smaller but some combinatorial problems involving them are becoming harder to solve. New families are facing harder planning and scheduling problems during Christmas and other holidays than their parents or grandparents ever did. Anyway, that’s an interesting way to explain what over-constrained problems and soft constraints are.

Suppose that you are the head of a family and you decide to run a party at Christmas evening or a banquet in the day after. One or two generations ago, it was not that hard: people used to live closer and have lots of children (I mean, more than two at least). In such case, it would not be a disaster if five out of your nine sons are not able to come over. It might be the case that families sharing common members agree on celebrating at different times. Anyway, the other parties would be so close to yours that everybody would eventually step by sometime.

However, with fewer children, people easily moving far away to pursue a career or for resting after retirement, divorced parents and grandparents running concurrent parties (maybe four grandparents married to four step-grandparents sharing a single grandchild), we must agree that pleasing everybody might become impossible.

That´s roughly what happens when some companies look for the help of an Operations Research consultant: they have a set of resources to produce goods or deliver services to their costumers and they are not sure if it became impossible to support the increasing demand with what they have or whether if they are only having a harder time to find a solution.

It might be the case that some constraints are not as important as it appeared to be. An over-constrained problem is said to be a problem upon which too many constraints are imposed, ruling out any possible solution. Looking carefully to the set of constraints, one might realize that some of them represent desirable but not mandatory situations, in which case they actually represent what we call soft constraints.

In the case of the families, what does a couple with no children and four parties in four cities at two different times do? At least in my case, we have to split in order to meet the scale. In the future, we aim at tackling this problem by running the party ourselves. 🙂

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Mathematical Modelling in Industry ’11 – first impressions

A conference about mathematical modelling in industry is going on at the University of São Paulo. I’m very impressed by the ambition of the event still on its first edition: three full days with three simultaneous tracks involving experienced speakers from varied countries. There are sessions about applications in flow simulation, new materials, aerospace, finance, medicine and much more. To be honest, I’ve no idea about many of the techniques mentioned on the abstracts of the program. I hope to leave the conference a bit more knowleadgeble about them. As usual in most of conferences I’ve been attending lately, I’m about to meet people working in my company that I’ve never heard about. I like it.

Despite everything I’ve written about, what really cheer me up about an event like this is that there is a huge gap between academia and industry in Brazil that we need to reduce.

If you want to know more about the event, check the website of the International Conference on Mathematical Modelling in Industry. If you are close by, the event is for free and you can register in the front desk.