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# D2 6th June 2013 Watch

1. I'm looking forward to FP1, instead of D2.

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2. (Original post by Arsey)
http://www.thestudentroom.co.uk/show....php?t=2013301

A revision thread I started last year. Contains lots of papers etc.

Here is a sheet of definitions; however, don't forget any definition from D1 'could' be asked.

absolutely hammer the 3 different LP questions; Allocation, Transportation, Game theory. One is guaranteed to come up and it is gift marks if revised properly.
Thanks so so much! That's great
3. Can someone please explain how to do this question please, in part B what does that notation even mean I cant figure it out by looking at the graph, and how do I do part C and express it in that form? also how do I find a max flow if I only have the capacities and not any flows which means I cant use the labelling procedure ?
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4. Why would player Y never play Y1??? says on mark scheme it shouldnt, im trying to do part B of question
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5. (Original post by Knoyle quiah)
Why would player Y never play Y1??? says on mark scheme it shouldnt, im trying to do part B of question
Not through domination. So it must be obvious from well graph. Lines l2 and l3 will always be the best option for Y

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6. (Original post by Arsey)
Not through domination. So it must be obvious from well graph. Lines l2 and l3 will always be the best option for Y

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Sorry I dont understand, do I draw another graph for player Y? i have attached the mark scheme, i couldnt find because of domination so didnt know why else
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7. (Original post by Knoyle quiah)
Sorry I dont understand, do I draw another graph for player Y? i have attached the mark scheme, i couldnt find because of domination so didnt know why else
The required intersection for X's optimal strategy is Y2 = Y3.
Therefore, if X is playing his optimal mixed strategy, Y should never play Y1.
8. (Original post by Epic Flawless)
The required intersection for X's optimal strategy is Y2 = Y3.
Therefore, if X is playing his optimal mixed strategy, Y should never play Y1.
Ok makes sense thanks
9. (Original post by Lilmzbest)
Game theory looks scary but actually isn't, it's just about learning how to set out a mixed strategy answer and then just practicing
yeah just got papers from my teacher. need to go through them. good luck
10. (Original post by Knoyle quiah)
Sorry I dont understand, do I draw another graph for player Y? i have attached the mark scheme, i couldnt find because of domination so didnt know why else
it is because if player X? is playing safe then his best option is to pick the highest point of the lowest lines, which in this case is where Y2 and Y3 meet. Therefore, Y should not play Y1.

Where is this question from?
11. (Original post by Arsey)
it is because if player X? is playing safe then his best option is to pick the highest point of the lowest lines, which in this case is where Y2 and Y3 meet. Therefore, Y should not play Y1.

Where is this question from?
Yeah makes sense, thanks. From the D2 solomon papers, but they dont have the new spec questions with network flows/simplex linear programming, where could I get some more of those questions? Seen some in the old D1 papers but what about OCR D2 would you say they are related to edexcel spec? (only network flows/simplex)
12. (Original post by Knoyle quiah)
Yeah makes sense, thanks. From the D2 solomon papers, but they dont have the new spec questions with network flows/simplex linear programming, where could I get some more of those questions? Seen some in the old D1 papers but what about OCR D2 would you say they are related to edexcel spec? (only network flows/simplex)
You could always do the D2 Solomon paper and take the simplex and network flow question from the corresponding D1 paper. I imagine the OCR questions would be fine as well for network flows and simplex.
13. (Original post by brittanna)
You could always do the D2 Solomon paper and take the simplex and network flow question from the corresponding D1 paper. I imagine the OCR questions would be fine as well for network flows and simplex.
Very good idea, might start doing that
14. (Original post by Knoyle quiah)
Why would player Y never play Y1??? says on mark scheme it shouldnt, im trying to do part B of question

(Original post by Arsey)
Not through domination. So it must be obvious from well graph. Lines l2 and l3 will always be the best option for Y

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Surely it is through domination? Y2 is always better than Y1 because the numbers are always smaller. From our perspective, Y's losses are shown, and Y2 is always less than Y1 so Y2 dominated Y1.

I suppose that can also be seen from the graph too.

-----------------------------

Anyway guys, I'm having trouble and I was wondering if you could help me.

Dynamic programming is fine when in graph form. But when it comes to these tables it is an absolute nightmare! Can anyone perhaps give me some strategies on how to identify what the stage, state, action and destination are?

Also there are some typical questions where some guy is travelling between countries, and the value is the profit subtract the travel costs or something.

However, which "end" do we add the profit on to?

Eg. Say I'm a singer on tour or something and I have to travel from A-B, then from B-C. Now say A-B and B-C both have travel costs of 10, but by visiting B I will make 100 from ticket prices.

My question is, when would I consider the ticket price in B? Would I say, A-B is -10 due to travel costs, +100 from the funds raised at B.

Or would I say, B-C is -10 due to travel costs, +100 raised from the funds at B. Do I consider the start vertex or end vertex?

Oh god I haven't explained myself well here, hopefully someone can still help, thanks.
15. (Original post by Hamburglar)
Surely it is through domination? Y2 is always better than Y1 because the numbers are always smaller. From our perspective, Y's losses are shown, and Y2 is always less than Y1 so Y2 dominated Y1.

I suppose that can also be seen from the graph too.

-----------------------------

Anyway guys, I'm having trouble and I was wondering if you could help me.

Dynamic programming is fine when in graph form. But when it comes to these tables it is an absolute nightmare! Can anyone perhaps give me some strategies on how to identify what the stage, state, action and destination are?

Also there are some typical questions where some guy is travelling between countries, and the value is the profit subtract the travel costs or something.

However, which "end" do we add the profit on to?

Eg. Say I'm a singer on tour or something and I have to travel from A-B, then from B-C. Now say A-B and B-C both have travel costs of 10, but by visiting B I will make 100 from ticket prices.

My question is, when would I consider the ticket price in B? Would I say, A-B is -10 due to travel costs, +100 from the funds raised at B.

Or would I say, B-C is -10 due to travel costs, +100 raised from the funds at B. Do I consider the start vertex or end vertex?

Oh god I haven't explained myself well here, hopefully someone can still help, thanks.
If the objective is to maximise profit, you would record the profit after each action. So the profit would be 100 - 10 = 90, You'd record that.
16. (Original post by Hamburglar)
Surely it is through domination? Y2 is always better than Y1 because the numbers are always smaller. From our perspective, Y's losses are shown, and Y2 is always less than Y1 so Y2 dominated Y1.

I suppose that can also be seen from the graph too.

-----------------------------

Anyway guys, I'm having trouble and I was wondering if you could help me.

Dynamic programming is fine when in graph form. But when it comes to these tables it is an absolute nightmare! Can anyone perhaps give me some strategies on how to identify what the stage, state, action and destination are?

Also there are some typical questions where some guy is travelling between countries, and the value is the profit subtract the travel costs or something.

However, which "end" do we add the profit on to?

Eg. Say I'm a singer on tour or something and I have to travel from A-B, then from B-C. Now say A-B and B-C both have travel costs of 10, but by visiting B I will make 100 from ticket prices.

My question is, when would I consider the ticket price in B? Would I say, A-B is -10 due to travel costs, +100 from the funds raised at B.

Or would I say, B-C is -10 due to travel costs, +100 raised from the funds at B. Do I consider the start vertex or end vertex?

Oh god I haven't explained myself well here, hopefully someone can still help, thanks.
I'm afraid i'm terrible lazy so just sorta skimmed through that (too many words )

I assume your asking about the dynamic programming questions where people travel between places and make money but then have to spend money on travelling and it all gets confusing

It doesn't matter which end (?) of the arc you consider, just choose one way and be consistent in your working, i personally add profits from the one you're leaving (in my head people get paid after doing work)
17. (Original post by Lilmzbest)
I'm afraid i'm terrible lazy so just sorta skimmed through that (too many words )

I assume your asking about the dynamic programming questions where people travel between places and make money but then have to spend money on travelling and it all gets confusing

It doesn't matter which end (?) of the arc you consider, just choose one way and be consistent in your working, i personally add profits from the one you're leaving (in my head people get paid after doing work)
Haha it's alright.

Yeah that and the whole, deciding what stage/state/action/destination actually is.

Oh so it doesn't matter which way you do it? That's awesome Yeah that's a good way of thinking about it, thanks! I was doing it the other way, where they got paid on arrival and in my first set of rows I had negative values, so I was confused. :s

Thanks for your help though
18. Since last year's dynamic programming was "make sth each month" and in 2011 was "traveling spent ". This this means they won't ask these two kinds of question this year?
19. (Original post by deansun)
Since last year's dynamic programming was "make sth each month" and in 2011 was "traveling spent ". This this means they won't ask these two kinds of question this year?
It often is like that, but i'd be safe and learn all of the types anyway, they might try to catch you out by doing another 'order book' type question, particularly since people tend to struggle with it
20. (Original post by deansun)
Since last year's dynamic programming was "make sth each month" and in 2011 was "traveling spent ". This this means they won't ask these two kinds of question this year?
I hope to god they don't. I find it strange that dynamic programming from a graph is much easier (personally anyway), and those wordy questions in table form are much harder. Yet the boundaries stay pretty consistent in D2. :s

I still can't get my head around what the stage and state and stuff should be

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Updated: June 11, 2013
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