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One Hull of A Rain Forest Green Computing Computer Science Neil Gordon January 14 2011

One Hull of A Rain Forest Green Computing Computer Science Neil Gordon January 14 2011. The Travelling Salesman problem. What is it?. Suppose Bob the salesman has been given a list of towns to visit to try selling his new products He knows how far it is from one town to the next

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One Hull of A Rain Forest Green Computing Computer Science Neil Gordon January 14 2011

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  1. One Hull of A Rain ForestGreen ComputingComputer ScienceNeil GordonJanuary 14 2011

  2. The Travelling Salesman problem

  3. What is it? • Suppose Bob the salesman has been given a list of towns to visit to try selling his new products • He knows how far it is from one town to the next • But wants to decide what is the best way to travel around them ? York Tickton 36 33 5 Beverley 48 4 7 Hull Change the way you think about Hull | 6 January 2011 | 3

  4. The Problem • Given a list of places (cities) with distances between, what is the shortest journey to travel to each location once only • It is hard – we will see how hard as we go through • It isn’t a new problem – it dates from the 1800s – when it was thought of by the mathematician William Hamilton – look him up on the Internet to find out more • Since then, it has been studied by mathematicians, computer scientists and lots of others…. Change the way you think about Hull | 4

  5. Why is Bob’s problem relevant to saving rainforests and your one hull of a Rainforest project? • There are a number of reasons – try listing them in your groups.Describe the reason, and why it is relevant to rainforests • Some of the reasons are: • Shorter journeys which saves • Time – for someone's job so that saves money as well • Fuel and resources – less travel means less petrol (or other fuel). That saves money AND helps to reduce the output of fossil fuels Change the way you think about Hull | 5

  6. Transport and the environment • Rainforests play a key role in the Earth’s eco-systems– who can explain what these are? • They provide habitats • They are the lungs of the planet, converting carbon-dioxide to oxygen. • However, rainforests face a number of challenges • acid rain – caused by pollution • climate change – the world seems to be getting hotter. Caused by pollution, especially transport….. Change the way you think about Hull | 6 January 2011 | 6

  7. How could you attempt to solve it • Given a simple example, try it in your groups using page 1 of the hand-outFirst for the maps with 3 towns • Then for the map with 4towns Beverley Beverley Tickton Paull 5 12 York 7 7 4 4 Tickton 36 33 5 Beverley 48 Hull Hull 4 7 Hull Change the way you think about Hull | 7

  8. How many possibilities are there? • How many possible routes could there be? • Suppose you have 2 places to visit • Or 3 places • Or 4 - In your groups, try to work this one out – do the routes for 5 places that is on the back of the handout • The answer is:see the next slide  Change the way you think about Hull | | 8

  9. Some example solutions • As the numbers get big, it quickly becomes hard to solveIf N=2 there are 2 possible routesif N=3 there are 6if N=4 there are 24What do you think for 5 places to visit? • if N=5 there are 120 different routesIf N=6 there would be 720 possible routesIt then gets much bigger very quickly…. • To visit the top 10 cities, there are 3628800 possible solutions. [This is assuming there is only 1 road between each city. If there were more, it gets harder to solve…] • To find the shortest route to visit the top 20 visitor attractions you would have to check 2432902008176640000 different routes. Even for a computer that takes a long time. Change the way you think about Hull | 6 January 2011 | 9

  10. Applications • Can you think of anything that needs to solve this type of problem a lot? • If your parents/carers/family have a SatNAV in their car, then that does this in the case where you want to travel between two places, sometimes with a third place to travel through. • This is still complicated – as there are lots of roads and they measure different things to find the best route • What criteria do they use to decide the best route? Change the way you think about Hull | | 10

  11. Solving the Travelling Salesman problem • The only way to guarantee the best solution is to try all possible routes • There are some different approaches to try to make it easier, for example • Start by only searching the shortest distances • Use tree searches and other approaches – if you do computing later in your studies you will meet these and learn how to go about solving these problems Change the way you think about Hull | 12

  12. What can you do to reduce your carbon footprint? • In your groups, identify 1 thing per person that you can do at school, at home or travelling between them to reduce your carbon footprint • Carbon calculator: http://www.cooltheworld.co.uk/kidscarbonquiz.html Change the way you think about Hull | 6 January 2011 | 14

  13. Summary • We have explored a few aspects of the Bob’s problem • We have seen that this is related to reducing the production of carbon and to helping protect the rain forests • We can use computers to help solve this sort of problem • Computers can help and assist in dealing with other problems too that can help in understanding and protecting the environment. Change the way you think about Hull | 6 January 2011 | 15

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