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PDS #3
| Question | Answer |
|---|---|
| Is there a unique model for each probelm? | no, the same real-worlds can be often modeled in different but equivalent ways |
| What is the sum of each column in incidence matrix | it is 0 |
| What is often better than writting x(i,j)>=0 as non-negativity condition | x(i,j) ∈Z+ only if only whole number are acceptable |
| What is the main difference between Minimum Cost Flow Problem and Transpoertation Problem | Transportation problem is special case of minimum cost flow with only supply and demand nodes MCFP also has transshipment nodes |
| What is notation for Integers in Mixed Integer Programming Problems | yi ∈ Z xi ∈ R (is for continuous variables) |
| What is general objective of Mixed Integer Problems | zMIP = max ∑c(i)*x(i) + ∑h(j)*y(j) |
| What are four basic types of number | N (natural numbers) = {1,2,..} Z (Integers) = {..-1,0,1...} Q (rational numbers) = {2/9 , 3/9, ..} "can be express as ratio of integers R (real numbers) = {e, pi} |
| What is the notation in The Knapsack Problem (4) | j ... Experiment that is or isnt taken w(j) .. weight of experiment j p(j) .. profit of experiment j C ... capacity of the knapsack |
| What are the decision variables in The Knapsack Problem | x(j) ∈ { 1, if j is taken 0, otherwise } |
| What are constrains in The Knapsack Problem (3) | x(j) ∈ {0;1} j ∈ {1; .. n of experiments} ∑ w(j) * x(j) <= C |
| What is objective function in The Knapsack Problem | z(x) = S⊆{j;..n} ∑p(j) z* = max z(x) |
| What is our goal in The Knapsack Problem | to get into our "bag" item combination with the highest profit possible |
| What is our goal in Bin Packing Problem | to get all the requiered item into as few bins as possible |
| How many bins do we have in a problem | number of bins = number of items |
| What are decision variables in Bin Packing Problem (2) | 1,(do we use bin j) yj = {1 if used , 0 otherwise } 2, (do we pack items i into bin j > xij = { 1 if packed, 0 otherwise} |
| What are 2 constrains in Bin Packing Problem | 1, Capacity constrains ∑w(i)*x(i,j) <= C(y(j)) capacity of bin j is not exeeded 2, Assigment constrains ∑ x(i,j) = 1 each item is exactly once given into a bin |
| What is objective function in Bin Packing Problem | min ∑y(j) |