Friday, 29 July 2011

I remember when networks used the mail

INFORMS asked us to blog about O.R. and Social Networks.

Once upon a time, O.R. people networked using the mail. In those days, academics would often have a network of people interested in the same branch of O.R., and would circulate drafts of papers by post for comment and criticism. And we networked at conferences, study groups and lectures.

When the OR Society (UK) held its conference in Exeter in 1991, they asked me to chair the event. I invited various speakers from outside the O.R. community to speak at the event. Two were academics. from geography and medicine. Independently they commented that the atmosphere of an O.R. conference was different from the experiences of their disciplines in conferences. They both said that it was much more friendly, and they sensed that O.R. people were less competitive. The networking was both social and sociable.

And then came USENET and the sci.op-research discussion group, which I followed and contributed to over the next ten years. It made for an international gathering, though there were the regular contributors who had a word to say about everything. There were those who thought that they could get help with student homework free of charge, and every so often we had contributions who thought that "op" meant "optical". On balance, I think that the overall cost-benefit of using the discussion group was limited. I could have done more usefully with my time than follow it. But there were days when it was valuable.

And now there are discussions of a kind on LinkedIn and Facebook relating to O.R.; very few people are contributing ... even to the group that hates linear programming.

As an example of a concept used in O.R., both of these recognise that their users form a graph, with each friendship represented by an edge between the nodes of people. So there are suggestions of people that you may know who are two edges away from you. I laugh at some of these. I am "friends" with my wife's sister and her children. But I don't know their circle of friends in the place where they live, even though Facebook tells me that we have many mutual friends. Facebook has an app which plots a friend graph, which in my case is reasonably small. It has several cliques. But I would know that without the app.

So, for O.R., following the new social networks are probably not cost-effective. All in all, I hope that O.R. people will continue to network at conferences, study groups and lectures, and that they will always be both social and sociable events.

Wednesday, 13 July 2011

The importance of experience

Three lessons were drummed into us as students of O.R., and I have tried to pass them on to my students.

(1) do not analyse numerical data by machine before you have looked at that data by hand; the analyst needs to have a "feel" for the numbers.
(2) do not assume that the decision-maker who is identified for you by the management is actually the decision-maker; somebody on the spot may actually take decisions which the management do not know about.
(3) observe as much of the system as possible, first hand. Walk the line!

On our trip last week to South Wales, the importance of number (3) became clear. But I doubt if the organisation actually has an O.R. team, but they needed O.R. advice.

We went out to an inn for our evening meal. Like most inns serving food, there was one queue for ordering food, and another for drinks. Food orders were passed to the kitchens and waiting staff, and drinks, of course, were served at once. However, on Wednesday evenings, it was Curry Night. If you ordered a curry at the food counter, then you could have a drink included in the price. This meant that the young lady at the food counter had to leave her place and collect the drink that you had ordered from her. Hence she had to do an increased workload on an evening when there was increased demand at the food queue. Customers for food had long queues, while there were no queues for drinks. Service time could be speeded up in various ways ... passing a token to the drinks bar ... having an extra person to serve at the food queue, all or some of the time. It could also be reduced by having a printed list of what "free drinks" were available, rather than for the staff to have to recite them. All of this could have been noticed if someone with authority had actually observed the queue process, rather than assume that the normal system could cope on the Curry Night.

Result: two very nice curries, reasonable drinks, but lost profits because we didn't go back to the long queue for a sweet.

Monday, 11 July 2011

Mini supermarkets

A news item at the weekend told that one of the big four UK supermarkets has opened a small city centre store for the first time. Morrisons were joining others (Tesco & Sainsbury and Co-operative) who have both large out-of-town stores and basic outlets in city centres.

The story claimed that the decision had been taken because of the recession, affecting the number of people who shop out-of-town. But the other stores know that there are different clienteles for different types of shop, so there is almost certainly an underlying decision to try and reach the clientele who shop regularly in their city centres. Maybe the recession drew the management's attention to the need to do this?

I don't know how many O.R. scientists work at Morrisons. But I hope that any who are there have read about a study that one of the others commissioned, which led to a change in the way that it handled distribution to its city-centre shops. The study showed that the principles of distribution were significantly different to such stores, compared with the model that was used for out-of-town stores. The O.R. person involved spent three months travelling in the cabs to observe what actually happened, which was not what the staff in head office thought happened. And as numerous O.R. studies have shown, it is always important for the O.R. staff to get involved on the front line, or sharp end.

What's in that truck?

Last week Tina and I drove from Exeter to South Wales for a two day break (it rained a lot!). On the motorway (M5) we started to pass the time by looking at the articulated lorries coming on the other carriageway. The first "game" was to look out for those labelled with the major British supermarkets. We decided that the rules were to see how long it took before we had a hand of five: Asda, Morrison, Sainsbury and Tesco, plus one wild card from Waitrose, Co-operative, Somerfield etc. We weren't sure whether or not to count M&S, as their lorries might be carrying clothes ... but decided that the big supermarkets also deal in clothes and much else. (Yes, British readers will know that Somerfield doesn't exist as an entity these days, but the Co-operative which has taken it over has not completed the conversion of its fleet. We even spotted a truck whose trailer read Somerfield, pulled by a tractor labelled Co-operative.)

In the first hour, we completed three hands of five, an indication of how much traffic there is into the south-west of England. But we were also interested in the other labelled food trucks. Once, when I was consulting for a major confectionery company, I remarked that you never saw lorries with their name on the side. I was told that when the company started in the UK, they linked to a local haulage company in the same town, and that haulage company continued to carry all the confectionery; the two companies had grown together. So there are many household names which never appear on the sides of articulated lorries in the UK.

But there were two companies we commented on, one selling yoghurts and dairy products, the other selling pasties and pies. How many yoghurts fit into a 40-ton trailer? Allowing for packaging and pallets, we suggested about 30,000 (assuming about 1kg each). And about the same time for the pies, possibly a few more. How many of these products would be sold in one day in a major supermarket? We estimated at least 10 and at most 1000, for both "large" and packages of four. So by the rules of guesstimation, we plumped for 100 per day (geometric mean). With two products, that meant each lorry carried enough for about 150 supermarkets. And with thousands of supermarkets across the country, one could see why it was economical for these companies to haul such large quantities of their products from factory to distribution centre in large trucks.

Next time we use the motorway, we'll be looking out for other named products on the move, and wondering whether the owners have made the decision to run their own fleets for commercial reasons or because it has "just happened".

Saturday, 2 July 2011

Networks and social networks

I was teaching a course on graphs and networks a few years ago, soon after Facebook became popular, and I mentioned that the graph of connections between the students in the room, defined by their Facebook "friends" would be an interesting one. Within 24 hours, several students had asked to be friends; I said that I felt it would compromise me to be linked to some but not all the class. However, we were able to discuss aspects of graph properties that related to Facebook.

I have a love of practical uses of graphs and networks, so was delighted to find a new one. It is the "Map of the World Drawn Entirely Using Facebook Connections" (found here among other places). Based on a large number of connections in Facebook, lines are drawn between them, and the colour of the line relates to the number of connections. Many people have links within their home city, still more are linked within their home country, and then there are international ones.

There are several fascinating aspects to the map. National coasts are very learly defined. Look at Florida, for instance. There are numerous links within the state, and these so outnumber the links to neighbouring states, that the coast of southern USA is clear. The same is true of the west of Britain. There are not many links between Wales and the west of England, so that the Bristol Channel is clearly marked. It is hard to see the boundaries between most countries, though Spain is clearly separated from France and Portugal, and (hardly surprisingly) the boundaries of Israel are well marked.

The author comments on the emptiness of China, Brazil and Russia. There are empty spaces in the world's deserts as well -- in Australia, the Sahara, and Central Asia.

The more I look at the map, the more I find of interest. A wonderful illustration of the power of mathematics and Operational Research.