6. Standard form-2 using Two-Phase method : Example-3
Find solution using Revised Simplex (Two-Phase) method MIN Z = 3x1 + 2x2 + x3 subject to x1 + x2 + x3 >= 4 x2 - x3 <= 2 x1 + x2 + 2x3 = 6 and x1,x2,x3 >= 0
Solution: Problem is
Min `Z` | `=` | `` | `3` | `x_1` | ` + ` | `2` | `x_2` | ` + ` | `` | `x_3` |
| subject to | `` | `` | `x_1` | ` + ` | `` | `x_2` | ` + ` | `` | `x_3` | ≥ | `4` | | | | `` | `` | `x_2` | ` - ` | `` | `x_3` | ≤ | `2` | `` | `` | `x_1` | ` + ` | `` | `x_2` | ` + ` | `2` | `x_3` | = | `6` |
| and `x_1,x_2,x_3 >= 0; ` |
`:.` Max `Z` | `=` | ` - ` | `3` | `x_1` | ` - ` | `2` | `x_2` | ` - ` | `` | `x_3` |
Step-1 : The problem is converted to canonical form by adding slack, surplus and artificial variables as appropiate
After introducing slack,surplus,artificial variables
`` | `` | `x_1` | ` + ` | `` | `x_2` | ` + ` | `` | `x_3` | ` - ` | `` | `S_1` | | | | ` + ` | `` | `A_1` | | | | = | `4` | | | | `` | `` | `x_2` | ` - ` | `` | `x_3` | | | | ` + ` | `` | `S_2` | | | | | | | = | `2` | `` | `` | `x_1` | ` + ` | `` | `x_2` | ` + ` | `2` | `x_3` | | | | | | | | | | ` + ` | `` | `A_2` | = | `6` |
|
The problem is converted to canonical form by adding slack, surplus and artificial variables as appropiate
After introducing slack,surplus,artificial variables
`` | `` | `Z'` | ` + ` | `3` | `x_1` | ` + ` | `2` | `x_2` | ` + ` | `` | `x_3` | | | | | | | | | | | | | | | | = | `0` | | | | ` - ` | `2` | `x_1` | ` - ` | `3` | `x_2` | ` - ` | `2` | `x_3` | ` + ` | `` | `S_1` | ` - ` | `` | `S_2` | | | | | | | ` + ` | `` | `x_5` | = | `-10` | | | | `` | `` | `x_1` | ` + ` | `` | `x_2` | ` + ` | `` | `x_3` | ` - ` | `` | `S_1` | | | | ` + ` | `` | `A_1` | | | | | | | = | `4` | | | | | | | `` | `` | `x_2` | ` - ` | `` | `x_3` | | | | ` + ` | `` | `S_2` | | | | | | | | | | = | `2` | | | | `` | `` | `x_1` | ` + ` | `` | `x_2` | ` + ` | `2` | `x_3` | | | | | | | | | | ` + ` | `` | `A_2` | | | | = | `6` |
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Now represent the new system of constraint equations in the matrix form `[[1,3,2,1,0,0,0,0,0],[0,-2,-3,-2,1,-1,0,0,1],[0,1,1,1,-1,0,1,0,0],[0,0,1,-1,0,1,0,0,0],[0,1,1,2,0,0,0,1,0]][[Z'],[x_1],[x_2],[x_3],[S_1],[S_2],[A_1],[A_2],[x_5]]=[[0],[-10],[4],[2],[6]]`
or `[[1,-c],[0,A]][[Z],[x]]=[[0,b]]; x>=0`
where `e=beta_0,a_5=beta_1,a_6=beta_2,a_7=beta_3,a_8=beta_4`
Step-2 : The basis matrix `B_1` of order `(4+1)=5` can be expressed as
`B_1=[beta_0,beta_1,beta_2,beta_3,beta_4]=[[1,0,0,0,0],[0,1,0,-1,0],[0,0,1,0,0],[0,0,0,1,0],[0,0,0,0,1]]`
Then, `B_1^(-1)=[[1,C_B B^(-1)],[0,B^(-1)]]=1; B=[[1,0,-1,0],[0,1,0,0],[0,0,1,0],[0,0,0,1]]=[beta_1,beta_2,beta_3,beta_4]; C_B=[0,0,0,0]`
Phase-1
| | Basis Inverse `B_1^(-1)` | | | Additional table | `B` | `X_B` | `beta_0` `Z'` | `beta_1` `x_5` | `beta_2` `A_1` | `beta_3` `S_2` | `beta_4` `A_2` | `y_1` `C_k-Z_k` | Min Ratio `(X_B)/(y_1)` | `x_1` | `x_2` | `x_3` | `S_1` | `Z'` | `0` | `1` | `0` | `0` | `0` | `0` | | --- | `3` | `2` | `1` | `0` | `x_5` | `-10` | `0` | `1` | `0` | `-1` | `0` | | --- | `-2` | `-3` | `-2` | `1` | `A_1` | `4` | `0` | `0` | `1` | `0` | `0` | | --- | `1` | `1` | `1` | `-1` | `S_2` | `2` | `0` | `0` | `0` | `1` | `0` | | --- | `0` | `1` | `-1` | `0` | `A_2` | `6` | `0` | `0` | `0` | `0` | `1` | | --- | `1` | `1` | `2` | `0` |
Iteration=1 : Repeat steps 3 to 5 to get new solution Step-3: To select the vector corresponding to a non-basic variable to enter into the basis, we compute `z_k-c_k="Min" {(z_j-c_j)<0;}`
`="Min"{(2^(nd)" row of " B_1^(-1)) ("Columns " a_j " not in basis")}`
`="Min"{[[0,1,0,-1,0]] [[3,2,1,0],[-2,-3,-2,1],[1,1,1,-1],[0,1,-1,0],[1,1,2,0]]}`
`="Min"{[[-2,-4,-1,1]]}`
`=-4` (correspnds to `z_2-c_2`)
Thus, vector `x_2` is selected to enter into the basis, for `k=2`
Step-4: To select a basic variable to leave the basis, we compute `y_k` for k=2, as follows
`y_2= B_1^(-1) a_2=[[1,0,0,0,0],[0,1,0,-1,0],[0,0,1,0,0],[0,0,0,1,0],[0,0,0,0,1]] [[2],[-3],[1],[1],[1]]=[[2],[-4],[1],[1],[1]]`
and `X_B = [[0],[-10],[4],[2],[6]]`
Now, calculate the minimum ratio to select the basic variable to leave the basis `x_(Br)/y_(rk)= "Min" {x_(Bi)/y_(ik), y_(ik)>0}`
`="Min"{(0)/(2),(4)/(1),(2)/(1),(6)/(1)}`
`="Min"{0,4,2,6}`
`=2 ("correspnds to " x_(B3)/y_(32))`
Thus, vector `S_2` is selected to leave the basis, for `r=3`
The table with new entries in column `y_2` and the minimum ratio
| | Basis Inverse `B_1^(-1)` | | | Additional table | `B` | `X_B` | `beta_0` `Z'` | `beta_1` `x_5` | `beta_2` `A_1` | `beta_3` `S_2` | `beta_4` `A_2` | `y_2` `C_k-Z_k` | Min Ratio `(X_B)/(y_2)` | `x_1` | `x_2` | `x_3` | `S_1` | `Z'` | `0` | `1` | `0` | `0` | `0` | `0` | `2` | `0` | `3` | `2` | `1` | `0` | `x_5` | `-10` | `0` | `1` | `0` | `-1` | `0` | `-4` | --- | `-2` | `-3` | `-2` | `1` | `A_1` | `4` | `0` | `0` | `1` | `0` | `0` | `1` | `4` | `1` | `1` | `1` | `-1` | `S_2` | `2` | `0` | `0` | `0` | `1` | `0` | `1` | `2` | `0` | `1` | `-1` | `0` | `A_2` | `6` | `0` | `0` | `0` | `0` | `1` | `1` | `6` | `1` | `1` | `2` | `0` |
The table solution is now updated by replacing variable `S_2` with the variable `x_2` into the basis.
For this we apply the following row operations in the same way as in the simplex method
| `X_B` | `beta_1` | `beta_2` | `beta_3` | `beta_4` | `y_2` | `R_1` | `0` | `0` | `0` | `0` | `0` | `2` | `R_2` | `-10` | `1` | `0` | `-1` | `0` | `-4` | `R_3` | `4` | `0` | `1` | `0` | `0` | `1` | `R_4` | `2` | `0` | `0` | `1` | `0` | `1` | `R_5` | `6` | `0` | `0` | `0` | `1` | `1` |
`R_4`(new)`= R_4`(old)`R_4`(old) = | `2` | | `0` | `0` | `1` | `0` | `R_4`(new)`= R_4`(old) | `2` | | `0` | `0` | `1` | `0` |
`R_1`(new)`= R_1`(old) - `2 R_4`(new)`R_1`(old) = | `0` | | `0` | `0` | `0` | `0` | `R_4`(new) = | `2` | | `0` | `0` | `1` | `0` | `2 xx R_4`(new) = | `4` | | `0` | `0` | `2` | `0` | `R_1`(new)`= R_1`(old) - `2 R_4`(new) | `-4` | | `0` | `0` | `-2` | `0` |
`R_2`(new)`= R_2`(old) + `4 R_4`(new)`R_2`(old) = | `-10` | | `1` | `0` | `-1` | `0` | `R_4`(new) = | `2` | | `0` | `0` | `1` | `0` | `4 xx R_4`(new) = | `8` | | `0` | `0` | `4` | `0` | `R_2`(new)`= R_2`(old) + `4 R_4`(new) | `-2` | | `1` | `0` | `3` | `0` |
`R_3`(new)`= R_3`(old) - `R_4`(new)`R_3`(old) = | `4` | | `0` | `1` | `0` | `0` | `R_4`(new) = | `2` | | `0` | `0` | `1` | `0` | `R_3`(new)`= R_3`(old) - `R_4`(new) | `2` | | `0` | `1` | `-1` | `0` |
`R_5`(new)`= R_5`(old) - `R_4`(new)`R_5`(old) = | `6` | | `0` | `0` | `0` | `1` | `R_4`(new) = | `2` | | `0` | `0` | `1` | `0` | `R_5`(new)`= R_5`(old) - `R_4`(new) | `4` | | `0` | `0` | `-1` | `1` |
The improved solution is
| | Basis Inverse `B_1^(-1)` | | | Additional table | `B` | `X_B` | `beta_0` `Z'` | `beta_1` `x_5` | `beta_2` `A_1` | `beta_3` `x_2` | `beta_4` `A_2` | `y_2` `C_k-Z_k` | Min Ratio `(X_B)/(y_2)` | `x_1` | `S_2` | `x_3` | `S_1` | `Z'` | `-4` | `1` | `0` | `0` | `-2` | `0` | | --- | `3` | `0` | `1` | `0` | `x_5` | `-2` | `0` | `1` | `0` | `3` | `0` | | --- | `-2` | `0` | `-2` | `1` | `A_1` | `2` | `0` | `0` | `1` | `-1` | `0` | | --- | `1` | `0` | `1` | `-1` | `x_2` | `2` | `0` | `0` | `0` | `1` | `0` | | --- | `0` | `1` | `-1` | `0` | `A_2` | `4` | `0` | `0` | `0` | `-1` | `1` | | --- | `1` | `0` | `2` | `0` |
Iteration=2 : Repeat steps 3 to 5 to get new solution Step-3: To select the vector corresponding to a non-basic variable to enter into the basis, we compute `z_k-c_k="Min" {(z_j-c_j)<0;}`
`="Min"{(2^(nd)" row of " B_1^(-1)) ("Columns " a_j " not in basis")}`
`="Min"{[[0,1,0,3,0]] [[3,0,1,0],[-2,0,-2,1],[1,0,1,-1],[0,1,-1,0],[1,0,2,0]]}`
`="Min"{[[-2,3,-5,1]]}`
`=-5` (correspnds to `z_3-c_3`)
Thus, vector `x_3` is selected to enter into the basis, for `k=3`
Step-4: To select a basic variable to leave the basis, we compute `y_k` for k=3, as follows
`y_3= B_1^(-1) a_3=[[1,0,0,-2,0],[0,1,0,3,0],[0,0,1,-1,0],[0,0,0,1,0],[0,0,0,-1,1]] [[1],[-2],[1],[-1],[2]]=[[3],[-5],[2],[-1],[3]]`
and `X_B = [[-4],[-2],[2],[2],[4]]`
Now, calculate the minimum ratio to select the basic variable to leave the basis `x_(Br)/y_(rk)= "Min" {x_(Bi)/y_(ik), y_(ik)>0}`
`="Min"{(-4)/(3),(2)/(2),(4)/(3)}`
`="Min"{-4/3,1,4/3}`
`=1 ("correspnds to " x_(B2)/y_(23))`
Thus, vector `A_1` is selected to leave the basis, for `r=2`
The table with new entries in column `y_3` and the minimum ratio
| | Basis Inverse `B_1^(-1)` | | | Additional table | `B` | `X_B` | `beta_0` `Z'` | `beta_1` `x_5` | `beta_2` `A_1` | `beta_3` `x_2` | `beta_4` `A_2` | `y_3` `C_k-Z_k` | Min Ratio `(X_B)/(y_3)` | `x_1` | `S_2` | `x_3` | `S_1` | `Z'` | `-4` | `1` | `0` | `0` | `-2` | `0` | `3` | `-4/3` | `3` | `0` | `1` | `0` | `x_5` | `-2` | `0` | `1` | `0` | `3` | `0` | `-5` | --- | `-2` | `0` | `-2` | `1` | `A_1` | `2` | `0` | `0` | `1` | `-1` | `0` | `2` | `1` | `1` | `0` | `1` | `-1` | `x_2` | `2` | `0` | `0` | `0` | `1` | `0` | `-1` | --- | `0` | `1` | `-1` | `0` | `A_2` | `4` | `0` | `0` | `0` | `-1` | `1` | `3` | `4/3` | `1` | `0` | `2` | `0` |
The table solution is now updated by replacing variable `A_1` with the variable `x_3` into the basis.
For this we apply the following row operations in the same way as in the simplex method
| `X_B` | `beta_1` | `beta_2` | `beta_3` | `beta_4` | `y_3` | `R_1` | `-4` | `0` | `0` | `-2` | `0` | `3` | `R_2` | `-2` | `1` | `0` | `3` | `0` | `-5` | `R_3` | `2` | `0` | `1` | `-1` | `0` | `2` | `R_4` | `2` | `0` | `0` | `1` | `0` | `-1` | `R_5` | `4` | `0` | `0` | `-1` | `1` | `3` |
`R_3`(new)`= R_3`(old)` -: 2``R_3`(old) = | `2` | | `0` | `1` | `-1` | `0` | `R_3`(new)`= R_3`(old)` -: 2` | `1` | | `0` | `1/2` | `-1/2` | `0` |
`R_1`(new)`= R_1`(old) - `3 R_3`(new)`R_1`(old) = | `-4` | | `0` | `0` | `-2` | `0` | `R_3`(new) = | `1` | | `0` | `1/2` | `-1/2` | `0` | `3 xx R_3`(new) = | `3` | | `0` | `3/2` | `-3/2` | `0` | `R_1`(new)`= R_1`(old) - `3 R_3`(new) | `-7` | | `0` | `-3/2` | `-1/2` | `0` |
`R_2`(new)`= R_2`(old) + `5 R_3`(new)`R_2`(old) = | `-2` | | `1` | `0` | `3` | `0` | `R_3`(new) = | `1` | | `0` | `1/2` | `-1/2` | `0` | `5 xx R_3`(new) = | `5` | | `0` | `5/2` | `-5/2` | `0` | `R_2`(new)`= R_2`(old) + `5 R_3`(new) | `3` | | `1` | `5/2` | `1/2` | `0` |
`R_4`(new)`= R_4`(old) + `R_3`(new)`R_4`(old) = | `2` | | `0` | `0` | `1` | `0` | `R_3`(new) = | `1` | | `0` | `1/2` | `-1/2` | `0` | `R_4`(new)`= R_4`(old) + `R_3`(new) | `3` | | `0` | `1/2` | `1/2` | `0` |
`R_5`(new)`= R_5`(old) - `3 R_3`(new)`R_5`(old) = | `4` | | `0` | `0` | `-1` | `1` | `R_3`(new) = | `1` | | `0` | `1/2` | `-1/2` | `0` | `3 xx R_3`(new) = | `3` | | `0` | `3/2` | `-3/2` | `0` | `R_5`(new)`= R_5`(old) - `3 R_3`(new) | `1` | | `0` | `-3/2` | `1/2` | `1` |
The improved solution is
| | Basis Inverse `B_1^(-1)` | | | Additional table | `B` | `X_B` | `beta_0` `Z'` | `beta_1` `x_5` | `beta_2` `x_3` | `beta_3` `x_2` | `beta_4` `A_2` | `y_3` `C_k-Z_k` | Min Ratio `(X_B)/(y_3)` | `x_1` | `S_2` | `A_1` | `S_1` | `Z'` | `-7` | `1` | `0` | `-3/2` | `-1/2` | `0` | | --- | `3` | `0` | `0` | `0` | `x_5` | `3` | `0` | `1` | `5/2` | `1/2` | `0` | | --- | `-2` | `0` | `0` | `1` | `x_3` | `1` | `0` | `0` | `1/2` | `-1/2` | `0` | | --- | `1` | `0` | `1` | `-1` | `x_2` | `3` | `0` | `0` | `1/2` | `1/2` | `0` | | --- | `0` | `1` | `0` | `0` | `A_2` | `1` | `0` | `0` | `-3/2` | `1/2` | `1` | | --- | `1` | `0` | `0` | `0` |
Iteration=3 : Repeat steps 3 to 5 to get new solution Step-3: To select the vector corresponding to a non-basic variable to enter into the basis, we compute `z_k-c_k="Min" {(z_j-c_j)<0;}`
`="Min"{(2^(nd)" row of " B_1^(-1)) ("Columns " a_j " not in basis")}`
`="Min"{[[0,1,5/2,1/2,0]] [[3,0,0,0],[-2,0,0,1],[1,0,1,-1],[0,1,0,0],[1,0,0,0]]}`
`="Min"{[[1/2,1/2,5/2,-3/2]]}`
`=-3/2` (correspnds to `z_4-c_4`)
Thus, vector `S_1` is selected to enter into the basis, for `k=4`
Step-4: To select a basic variable to leave the basis, we compute `y_k` for k=4, as follows
`y_4= B_1^(-1) a_4=[[1,0,-3/2,-1/2,0],[0,1,5/2,1/2,0],[0,0,1/2,-1/2,0],[0,0,1/2,1/2,0],[0,0,-3/2,1/2,1]] [[0],[1],[-1],[0],[0]]=[[3/2],[-3/2],[-1/2],[-1/2],[3/2]]`
and `X_B = [[-7],[3],[1],[3],[1]]`
Now, calculate the minimum ratio to select the basic variable to leave the basis `x_(Br)/y_(rk)= "Min" {x_(Bi)/y_(ik), y_(ik)>0}`
`="Min"{(-7)/(3/2),(1)/(3/2)}`
`="Min"{-14/3,2/3}`
`=2/3 ("correspnds to " x_(B4)/y_(44))`
Thus, vector `A_2` is selected to leave the basis, for `r=4`
The table with new entries in column `y_4` and the minimum ratio
| | Basis Inverse `B_1^(-1)` | | | Additional table | `B` | `X_B` | `beta_0` `Z'` | `beta_1` `x_5` | `beta_2` `x_3` | `beta_3` `x_2` | `beta_4` `A_2` | `y_4` `C_k-Z_k` | Min Ratio `(X_B)/(y_4)` | `x_1` | `S_2` | `A_1` | `S_1` | `Z'` | `-7` | `1` | `0` | `-3/2` | `-1/2` | `0` | `3/2` | `-14/3` | `3` | `0` | `0` | `0` | `x_5` | `3` | `0` | `1` | `5/2` | `1/2` | `0` | `-3/2` | --- | `-2` | `0` | `0` | `1` | `x_3` | `1` | `0` | `0` | `1/2` | `-1/2` | `0` | `-1/2` | --- | `1` | `0` | `1` | `-1` | `x_2` | `3` | `0` | `0` | `1/2` | `1/2` | `0` | `-1/2` | --- | `0` | `1` | `0` | `0` | `A_2` | `1` | `0` | `0` | `-3/2` | `1/2` | `1` | `3/2` | `2/3` | `1` | `0` | `0` | `0` |
The table solution is now updated by replacing variable `A_2` with the variable `S_1` into the basis.
For this we apply the following row operations in the same way as in the simplex method
| `X_B` | `beta_1` | `beta_2` | `beta_3` | `beta_4` | `y_4` | `R_1` | `-7` | `0` | `-3/2` | `-1/2` | `0` | `3/2` | `R_2` | `3` | `1` | `5/2` | `1/2` | `0` | `-3/2` | `R_3` | `1` | `0` | `1/2` | `-1/2` | `0` | `-1/2` | `R_4` | `3` | `0` | `1/2` | `1/2` | `0` | `-1/2` | `R_5` | `1` | `0` | `-3/2` | `1/2` | `1` | `3/2` |
`R_5`(new)`= R_5`(old) `xx2/3``R_5`(old) = | `1` | | `0` | `-3/2` | `1/2` | `1` | `R_5`(new)`= R_5`(old) `xx2/3` | `2/3` | | `0` | `-1` | `1/3` | `2/3` |
`R_1`(new)`= R_1`(old) - `3/2 R_5`(new)`R_1`(old) = | `-7` | | `0` | `-3/2` | `-1/2` | `0` | `R_5`(new) = | `2/3` | | `0` | `-1` | `1/3` | `2/3` | `3/2 xx R_5`(new) = | `1` | | `0` | `-3/2` | `1/2` | `1` | `R_1`(new)`= R_1`(old) - `3/2 R_5`(new) | `-8` | | `0` | `0` | `-1` | `-1` |
`R_2`(new)`= R_2`(old) + `3/2 R_5`(new)`R_2`(old) = | `3` | | `1` | `5/2` | `1/2` | `0` | `R_5`(new) = | `2/3` | | `0` | `-1` | `1/3` | `2/3` | `3/2 xx R_5`(new) = | `1` | | `0` | `-3/2` | `1/2` | `1` | `R_2`(new)`= R_2`(old) + `3/2 R_5`(new) | `4` | | `1` | `1` | `1` | `1` |
`R_3`(new)`= R_3`(old) + `1/2 R_5`(new)`R_3`(old) = | `1` | | `0` | `1/2` | `-1/2` | `0` | `R_5`(new) = | `2/3` | | `0` | `-1` | `1/3` | `2/3` | `1/2 xx R_5`(new) = | `1/3` | | `0` | `-1/2` | `1/6` | `1/3` | `R_3`(new)`= R_3`(old) + `1/2 R_5`(new) | `4/3` | | `0` | `0` | `-1/3` | `1/3` |
`R_4`(new)`= R_4`(old) + `1/2 R_5`(new)`R_4`(old) = | `3` | | `0` | `1/2` | `1/2` | `0` | `R_5`(new) = | `2/3` | | `0` | `-1` | `1/3` | `2/3` | `1/2 xx R_5`(new) = | `1/3` | | `0` | `-1/2` | `1/6` | `1/3` | `R_4`(new)`= R_4`(old) + `1/2 R_5`(new) | `10/3` | | `0` | `0` | `2/3` | `1/3` |
The improved solution is
| | Basis Inverse `B_1^(-1)` | | | Additional table | `B` | `X_B` | `beta_0` `Z'` | `beta_1` `x_5` | `beta_2` `x_3` | `beta_3` `x_2` | `beta_4` `S_1` | `y_4` `C_k-Z_k` | Min Ratio `(X_B)/(y_4)` | `x_1` | `S_2` | `A_1` | `A_2` | `Z'` | `-8` | `1` | `0` | `0` | `-1` | `-1` | | --- | `3` | `0` | `0` | `0` | `x_5` | `4` | `0` | `1` | `1` | `1` | `1` | | --- | `-2` | `0` | `0` | `0` | `x_3` | `4/3` | `0` | `0` | `0` | `-1/3` | `1/3` | | --- | `1` | `0` | `1` | `0` | `x_2` | `10/3` | `0` | `0` | `0` | `2/3` | `1/3` | | --- | `0` | `1` | `0` | `0` | `S_1` | `2/3` | `0` | `0` | `-1` | `1/3` | `2/3` | | --- | `1` | `0` | `0` | `1` |
Iteration=4 : Repeat steps 3 to 5 to get new solution Step-3: To select the vector corresponding to a non-basic variable to enter into the basis, we compute `z_k-c_k="Min" {(z_j-c_j)<0;}`
`="Min"{(2^(nd)" row of " B_1^(-1)) ("Columns " a_j " not in basis")}`
`="Min"{[[0,1,1,1,1]] [[3,0,0,0],[-2,0,0,0],[1,0,1,0],[0,1,0,0],[1,0,0,1]]}`
`="Min"{[[0,1,1,1]]}`
Since all `Z_j-C_j >= 0`
Hence, optimal solution is arrived with value of variables as : `x_1=0,x_2=10/3,x_3=4/3`
Max `Z=-8`
`:.` Min `Z=8`
Phase-2 We maximize `Z'` instead of `x_5`
Artificial variables will be removed from additional table
| | Basis Inverse `B_1^(-1)` | | | Additional table | `B` | `X_B` | `beta_0` `Z'` | `beta_1` `x_5` | `beta_2` `x_3` | `beta_3` `x_2` | `beta_4` `S_1` | `y_0` `C_k-Z_k` | Min Ratio `(X_B)/(y_0)` | `x_1` | `S_2` | `Z'` | `-8` | `1` | `0` | `0` | `-1` | `-1` | | --- | `3` | `0` | `x_5` | `4` | `0` | `1` | `1` | `1` | `1` | | --- | `-2` | `0` | `x_3` | `4/3` | `0` | `0` | `0` | `-1/3` | `1/3` | | --- | `1` | `0` | `x_2` | `10/3` | `0` | `0` | `0` | `2/3` | `1/3` | | --- | `0` | `1` | `S_1` | `2/3` | `0` | `0` | `-1` | `1/3` | `2/3` | | --- | `1` | `0` |
Iteration=1 : Repeat steps 3 to 5 to get new solution Step-3: To select the vector corresponding to a non-basic variable to enter into the basis, we compute `z_k-c_k="Min" {(z_j-c_j)<0;}`
`="Min"{(1^(st)" row of " B_1^(-1)) ("Columns " a_j " not in basis")}`
`="Min"{[[1,0,0,-1,-1]] [[3,0],[-2,0],[1,0],[0,1],[1,0]]}`
`="Min"{[[2,-1]]}`
`=-1` (correspnds to `z_2-c_2`)
Thus, vector `S_2` is selected to enter into the basis, for `k=2`
Step-4: To select a basic variable to leave the basis, we compute `y_k` for k=2, as follows
`y_2= B_1^(-1) a_2=[[1,0,0,-1,-1],[0,1,1,1,1],[0,0,0,-1/3,1/3],[0,0,0,2/3,1/3],[0,0,-1,1/3,2/3]] [[0],[0],[0],[1],[0]]=[[-1],[1],[-1/3],[2/3],[1/3]]`
and `X_B = [[-8],[4],[4/3],[10/3],[2/3]]`
Now, calculate the minimum ratio to select the basic variable to leave the basis `x_(Br)/y_(rk)= "Min" {x_(Bi)/y_(ik), y_(ik)>0}`
`="Min"{(4)/(1),(10/3)/(2/3),(2/3)/(1/3)}`
`="Min"{4,5,2}`
`=2 ("correspnds to " x_(B4)/y_(42))`
Thus, vector `S_1` is selected to leave the basis, for `r=4`
The table with new entries in column `y_2` and the minimum ratio
| | Basis Inverse `B_1^(-1)` | | | Additional table | `B` | `X_B` | `beta_0` `Z'` | `beta_1` `x_5` | `beta_2` `x_3` | `beta_3` `x_2` | `beta_4` `S_1` | `y_2` `C_k-Z_k` | Min Ratio `(X_B)/(y_2)` | `x_1` | `S_2` | `Z'` | `-8` | `1` | `0` | `0` | `-1` | `-1` | `-1` | --- | `3` | `0` | `x_5` | `4` | `0` | `1` | `1` | `1` | `1` | `1` | `4` | `-2` | `0` | `x_3` | `4/3` | `0` | `0` | `0` | `-1/3` | `1/3` | `-1/3` | --- | `1` | `0` | `x_2` | `10/3` | `0` | `0` | `0` | `2/3` | `1/3` | `2/3` | `5` | `0` | `1` | `S_1` | `2/3` | `0` | `0` | `-1` | `1/3` | `2/3` | `1/3` | `2` | `1` | `0` |
The table solution is now updated by replacing variable `S_1` with the variable `S_2` into the basis.
For this we apply the following row operations in the same way as in the simplex method
| `X_B` | `beta_1` | `beta_2` | `beta_3` | `beta_4` | `y_2` | `R_1` | `-8` | `0` | `0` | `-1` | `-1` | `-1` | `R_2` | `4` | `1` | `1` | `1` | `1` | `1` | `R_3` | `4/3` | `0` | `0` | `-1/3` | `1/3` | `-1/3` | `R_4` | `10/3` | `0` | `0` | `2/3` | `1/3` | `2/3` | `R_5` | `2/3` | `0` | `-1` | `1/3` | `2/3` | `1/3` |
`R_5`(new)`= R_5`(old) `xx3``R_5`(old) = | `2/3` | | `0` | `-1` | `1/3` | `2/3` | `R_5`(new)`= R_5`(old) `xx3` | `2` | | `0` | `-3` | `1` | `2` |
`R_1`(new)`= R_1`(old) + `R_5`(new)`R_1`(old) = | `-8` | | `0` | `0` | `-1` | `-1` | `R_5`(new) = | `2` | | `0` | `-3` | `1` | `2` | `R_1`(new)`= R_1`(old) + `R_5`(new) | `-6` | | `0` | `-3` | `0` | `1` |
`R_2`(new)`= R_2`(old) - `R_5`(new)`R_2`(old) = | `4` | | `1` | `1` | `1` | `1` | `R_5`(new) = | `2` | | `0` | `-3` | `1` | `2` | `R_2`(new)`= R_2`(old) - `R_5`(new) | `2` | | `1` | `4` | `0` | `-1` |
`R_3`(new)`= R_3`(old) + `1/3 R_5`(new)`R_3`(old) = | `4/3` | | `0` | `0` | `-1/3` | `1/3` | `R_5`(new) = | `2` | | `0` | `-3` | `1` | `2` | `1/3 xx R_5`(new) = | `2/3` | | `0` | `-1` | `1/3` | `2/3` | `R_3`(new)`= R_3`(old) + `1/3 R_5`(new) | `2` | | `0` | `-1` | `0` | `1` |
`R_4`(new)`= R_4`(old) - `2/3 R_5`(new)`R_4`(old) = | `10/3` | | `0` | `0` | `2/3` | `1/3` | `R_5`(new) = | `2` | | `0` | `-3` | `1` | `2` | `2/3 xx R_5`(new) = | `4/3` | | `0` | `-2` | `2/3` | `4/3` | `R_4`(new)`= R_4`(old) - `2/3 R_5`(new) | `2` | | `0` | `2` | `0` | `-1` |
The improved solution is
| | Basis Inverse `B_1^(-1)` | | | Additional table | `B` | `X_B` | `beta_0` `Z'` | `beta_1` `x_5` | `beta_2` `x_3` | `beta_3` `x_2` | `beta_4` `S_2` | `y_2` `C_k-Z_k` | Min Ratio `(X_B)/(y_2)` | `x_1` | `S_1` | `Z'` | `-6` | `1` | `0` | `-3` | `0` | `1` | | --- | `3` | `0` | `x_5` | `2` | `0` | `1` | `4` | `0` | `-1` | | --- | `-2` | `0` | `x_3` | `2` | `0` | `0` | `-1` | `0` | `1` | | --- | `1` | `0` | `x_2` | `2` | `0` | `0` | `2` | `0` | `-1` | | --- | `0` | `0` | `S_2` | `2` | `0` | `0` | `-3` | `1` | `2` | | --- | `1` | `1` |
Iteration=2 : Repeat steps 3 to 5 to get new solution Step-3: To select the vector corresponding to a non-basic variable to enter into the basis, we compute `z_k-c_k="Min" {(z_j-c_j)<0;}`
`="Min"{(1^(st)" row of " B_1^(-1)) ("Columns " a_j " not in basis")}`
`="Min"{[[1,0,-3,0,1]] [[3,0],[-2,0],[1,0],[0,0],[1,1]]}`
`="Min"{[[1,1]]}`
Since all `Z_j-C_j >= 0`
Hence, optimal solution is arrived with value of variables as : `x_1=0,x_2=2,x_3=2`
Max `Z=-6`
`:.` Min `Z=6`
This material is intended as a summary. Use your textbook for detail explanation. Any bug, improvement, feedback then
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