3. Unbalanced supply and demand example
Unbalanced supply and demand
If the total supply is not equal to the total demand then the problem is called unbalanced transportation problem.
It's solution :
1. If the total supply is more than the total demand, then we add a new column, with transportation cost 0
2. If the total demand is more than the total supply, then we add a new row, with transportation cost 0
Example
Find Solution using Russell's Approximation method
| D1 | D2 | D3 | Supply | S1 | 4 | 8 | 8 | 76 | S2 | 16 | 24 | 16 | 82 | S3 | 8 | 16 | 24 | 77 | Demand | 72 | 102 | 41 | |
Solution: TOTAL number of supply constraints : 3 TOTAL number of demand constraints : 3 Problem Table is
| `D_1` | `D_2` | `D_3` | | Supply | `S_1` | 4 | 8 | 8 | | 76 | `S_2` | 16 | 24 | 16 | | 82 | `S_3` | 8 | 16 | 24 | | 77 | | Demand | 72 | 102 | 41 | | |
Here Total Demand = 215 is less than Total Supply = 235. So We add a dummy demand constraint with 0 unit cost and with allocation 20. Now, The modified table is
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4 | 8 | 8 | 0 | | 76 | `S_2` | 16 | 24 | 16 | 0 | | 82 | `S_3` | 8 | 16 | 24 | 0 | | 77 | | Demand | 72 | 102 | 41 | 20 | | |
Table-1: Calculate `bar U_i` and `bar V_j` (where `bar U_i` is the largest cost in row and `bar V_j` is the largest cost in column)
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `bar U_i` | `S_1` | 4 | 8 | 8 | 0 | | 76 | `8` | `S_2` | 16 | 24 | 16 | 0 | | 82 | `24` | `S_3` | 8 | 16 | 24 | 0 | | 77 | `24` | | Demand | 72 | 102 | 41 | 20 | | | | `bar V_j` | `16` | `24` | `24` | `0` | | | |
2. Compute reduced cost of each cell `Delta_(ij)`, where `Delta_(ij) = c_(ij) - (bar U_i + bar V_j)`
`1. Delta_11 = c_11 - (bar U_1 + bar V_1) = 4 - (8 +16) = color{blue}{-20} `
`2. Delta_12 = c_12 - (bar U_1 + bar V_2) = 8 - (8 +24) = color{blue}{-24} `
`3. Delta_13 = c_13 - (bar U_1 + bar V_3) = 8 - (8 +24) = color{blue}{-24} `
`4. Delta_14 = c_14 - (bar U_1 + bar V_4) = 0 - (8 +0) = color{blue}{-8} `
`5. Delta_21 = c_21 - (bar U_2 + bar V_1) = 16 - (24 +16) = color{blue}{-24} `
`6. Delta_22 = c_22 - (bar U_2 + bar V_2) = 24 - (24 +24) = color{blue}{-24} `
`7. Delta_23 = c_23 - (bar U_2 + bar V_3) = 16 - (24 +24) = color{blue}{-32} `
`8. Delta_24 = c_24 - (bar U_2 + bar V_4) = 0 - (24 +0) = color{blue}{-24} `
`9. Delta_31 = c_31 - (bar U_3 + bar V_1) = 8 - (24 +16) = color{blue}{-32} `
`10. Delta_32 = c_32 - (bar U_3 + bar V_2) = 16 - (24 +24) = color{blue}{-32} `
`11. Delta_33 = c_33 - (bar U_3 + bar V_3) = 24 - (24 +24) = color{blue}{-24} `
`12. Delta_34 = c_34 - (bar U_3 + bar V_4) = 0 - (24 +0) = color{blue}{-24} `
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `bar U_i` | `S_1` | 4 [-20] | 8 [-24] | 8 [-24] | 0 [-8] | | 76 | `8` | `S_2` | 16 [-24] | 24 [-24] | 16 [-32] | 0 [-24] | | 82 | `24` | `S_3` | 8 [-32] | 16 [-32] | 24 [-24] | 0 [-24] | | 77 | `24` | | Demand | 72 | 102 | 41 | 20 | | | | `bar V_j` | `16` | `24` | `24` | `0` | | | |
The most negative `Delta_(ij)` is -32 in cell `S_3 D_2`
The allocation to this cell is min(77,102) = 77. This exhausts the capacity of `S_3` and leaves 102 - 77 = 25 units with `D_2`
Table-1: This leads to the following table
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4 | 8 | 8 | 0 | | 76 | `S_2` | 16 | 24 | 16 | 0 | | 82 | `S_3` | 8 | 16 (77) | 24 | 0 | | 0 | | Demand | 72 | 25 | 41 | 20 | | |
Table-2: Calculate `bar U_i` and `bar V_j` (where `bar U_i` is the largest cost in row and `bar V_j` is the largest cost in column)
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `bar U_i` | `S_1` | 4 | 8 | 8 | 0 | | 76 | `8` | `S_2` | 16 | 24 | 16 | 0 | | 82 | `24` | `S_3` | 8 | 16(77) | 24 | 0 | | 0 | -- | | Demand | 72 | 25 | 41 | 20 | | | | `bar V_j` | `16` | `24` | `16` | `0` | | | |
2. Compute reduced cost of each cell `Delta_(ij)`, where `Delta_(ij) = c_(ij) - (bar U_i + bar V_j)`
`1. Delta_11 = c_11 - (bar U_1 + bar V_1) = 4 - (8 +16) = color{blue}{-20} `
`2. Delta_12 = c_12 - (bar U_1 + bar V_2) = 8 - (8 +24) = color{blue}{-24} `
`3. Delta_13 = c_13 - (bar U_1 + bar V_3) = 8 - (8 +16) = color{blue}{-16} `
`4. Delta_14 = c_14 - (bar U_1 + bar V_4) = 0 - (8 +0) = color{blue}{-8} `
`5. Delta_21 = c_21 - (bar U_2 + bar V_1) = 16 - (24 +16) = color{blue}{-24} `
`6. Delta_22 = c_22 - (bar U_2 + bar V_2) = 24 - (24 +24) = color{blue}{-24} `
`7. Delta_23 = c_23 - (bar U_2 + bar V_3) = 16 - (24 +16) = color{blue}{-24} `
`8. Delta_24 = c_24 - (bar U_2 + bar V_4) = 0 - (24 +0) = color{blue}{-24} `
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `bar U_i` | `S_1` | 4 [-20] | 8 [-24] | 8 [-16] | 0 [-8] | | 76 | `8` | `S_2` | 16 [-24] | 24 [-24] | 16 [-24] | 0 [-24] | | 82 | `24` | `S_3` | 8 | 16(77) | 24 | 0 | | 0 | -- | | Demand | 72 | 25 | 41 | 20 | | | | `bar V_j` | `16` | `24` | `16` | `0` | | | |
The most negative `Delta_(ij)` is -24 in cell `S_2 D_(dummy)`
The allocation to this cell is min(82,20) = 20. This satisfies the entire demand of `D_(dummy)` and leaves 82 - 20 = 62 units with `S_2`
Table-2: This leads to the following table
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4 | 8 | 8 | 0 | | 76 | `S_2` | 16 | 24 | 16 | 0 (20) | | 62 | `S_3` | 8 | 16 (77) | 24 | 0 | | 0 | | Demand | 72 | 25 | 41 | 0 | | |
Table-3: Calculate `bar U_i` and `bar V_j` (where `bar U_i` is the largest cost in row and `bar V_j` is the largest cost in column)
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `bar U_i` | `S_1` | 4 | 8 | 8 | 0 | | 76 | `8` | `S_2` | 16 | 24 | 16 | 0(20) | | 62 | `24` | `S_3` | 8 | 16(77) | 24 | 0 | | 0 | -- | | Demand | 72 | 25 | 41 | 0 | | | | `bar V_j` | `16` | `24` | `16` | -- | | | |
2. Compute reduced cost of each cell `Delta_(ij)`, where `Delta_(ij) = c_(ij) - (bar U_i + bar V_j)`
`1. Delta_11 = c_11 - (bar U_1 + bar V_1) = 4 - (8 +16) = color{blue}{-20} `
`2. Delta_12 = c_12 - (bar U_1 + bar V_2) = 8 - (8 +24) = color{blue}{-24} `
`3. Delta_13 = c_13 - (bar U_1 + bar V_3) = 8 - (8 +16) = color{blue}{-16} `
`4. Delta_21 = c_21 - (bar U_2 + bar V_1) = 16 - (24 +16) = color{blue}{-24} `
`5. Delta_22 = c_22 - (bar U_2 + bar V_2) = 24 - (24 +24) = color{blue}{-24} `
`6. Delta_23 = c_23 - (bar U_2 + bar V_3) = 16 - (24 +16) = color{blue}{-24} `
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `bar U_i` | `S_1` | 4 [-20] | 8 [-24] | 8 [-16] | 0 | | 76 | `8` | `S_2` | 16 [-24] | 24 [-24] | 16 [-24] | 0(20) | | 62 | `24` | `S_3` | 8 | 16(77) | 24 | 0 | | 0 | -- | | Demand | 72 | 25 | 41 | 0 | | | | `bar V_j` | `16` | `24` | `16` | -- | | | |
The most negative `Delta_(ij)` is -24 in cell `S_2 D_1`
The allocation to this cell is min(62,72) = 62. This exhausts the capacity of `S_2` and leaves 72 - 62 = 10 units with `D_1`
Table-3: This leads to the following table
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4 | 8 | 8 | 0 | | 76 | `S_2` | 16 (62) | 24 | 16 | 0 (20) | | 0 | `S_3` | 8 | 16 (77) | 24 | 0 | | 0 | | Demand | 10 | 25 | 41 | 0 | | |
Table-4: Calculate `bar U_i` and `bar V_j` (where `bar U_i` is the largest cost in row and `bar V_j` is the largest cost in column)
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `bar U_i` | `S_1` | 4 | 8 | 8 | 0 | | 76 | `8` | `S_2` | 16(62) | 24 | 16 | 0(20) | | 0 | -- | `S_3` | 8 | 16(77) | 24 | 0 | | 0 | -- | | Demand | 10 | 25 | 41 | 0 | | | | `bar V_j` | `4` | `8` | `8` | -- | | | |
2. Compute reduced cost of each cell `Delta_(ij)`, where `Delta_(ij) = c_(ij) - (bar U_i + bar V_j)`
`1. Delta_11 = c_11 - (bar U_1 + bar V_1) = 4 - (8 +4) = color{blue}{-8} `
`2. Delta_12 = c_12 - (bar U_1 + bar V_2) = 8 - (8 +8) = color{blue}{-8} `
`3. Delta_13 = c_13 - (bar U_1 + bar V_3) = 8 - (8 +8) = color{blue}{-8} `
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `bar U_i` | `S_1` | 4 [-8] | 8 [-8] | 8 [-8] | 0 | | 76 | `8` | `S_2` | 16(62) | 24 | 16 | 0(20) | | 0 | -- | `S_3` | 8 | 16(77) | 24 | 0 | | 0 | -- | | Demand | 10 | 25 | 41 | 0 | | | | `bar V_j` | `4` | `8` | `8` | -- | | | |
The most negative `Delta_(ij)` is -8 in cell `S_1 D_3`
The allocation to this cell is min(76,41) = 41. This satisfies the entire demand of `D_3` and leaves 76 - 41 = 35 units with `S_1`
Table-4: This leads to the following table
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4 | 8 | 8 (41) | 0 | | 35 | `S_2` | 16 (62) | 24 | 16 | 0 (20) | | 0 | `S_3` | 8 | 16 (77) | 24 | 0 | | 0 | | Demand | 10 | 25 | 0 | 0 | | |
Table-5: Calculate `bar U_i` and `bar V_j` (where `bar U_i` is the largest cost in row and `bar V_j` is the largest cost in column)
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `bar U_i` | `S_1` | 4 | 8 | 8(41) | 0 | | 35 | `8` | `S_2` | 16(62) | 24 | 16 | 0(20) | | 0 | -- | `S_3` | 8 | 16(77) | 24 | 0 | | 0 | -- | | Demand | 10 | 25 | 0 | 0 | | | | `bar V_j` | `4` | `8` | -- | -- | | | |
2. Compute reduced cost of each cell `Delta_(ij)`, where `Delta_(ij) = c_(ij) - (bar U_i + bar V_j)`
`1. Delta_11 = c_11 - (bar U_1 + bar V_1) = 4 - (8 +4) = color{blue}{-8} `
`2. Delta_12 = c_12 - (bar U_1 + bar V_2) = 8 - (8 +8) = color{blue}{-8} `
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `bar U_i` | `S_1` | 4 [-8] | 8 [-8] | 8(41) | 0 | | 35 | `8` | `S_2` | 16(62) | 24 | 16 | 0(20) | | 0 | -- | `S_3` | 8 | 16(77) | 24 | 0 | | 0 | -- | | Demand | 10 | 25 | 0 | 0 | | | | `bar V_j` | `4` | `8` | -- | -- | | | |
The most negative `Delta_(ij)` is -8 in cell `S_1 D_2`
The allocation to this cell is min(35,25) = 25. This satisfies the entire demand of `D_2` and leaves 35 - 25 = 10 units with `S_1`
Table-5: This leads to the following table
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4 | 8 (25) | 8 (41) | 0 | | 10 | `S_2` | 16 (62) | 24 | 16 | 0 (20) | | 0 | `S_3` | 8 | 16 (77) | 24 | 0 | | 0 | | Demand | 10 | 0 | 0 | 0 | | |
Table-6: Calculate `bar U_i` and `bar V_j` (where `bar U_i` is the largest cost in row and `bar V_j` is the largest cost in column)
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `bar U_i` | `S_1` | 4 | 8(25) | 8(41) | 0 | | 10 | `4` | `S_2` | 16(62) | 24 | 16 | 0(20) | | 0 | -- | `S_3` | 8 | 16(77) | 24 | 0 | | 0 | -- | | Demand | 10 | 0 | 0 | 0 | | | | `bar V_j` | `4` | -- | -- | -- | | | |
2. Compute reduced cost of each cell `Delta_(ij)`, where `Delta_(ij) = c_(ij) - (bar U_i + bar V_j)`
`1. Delta_11 = c_11 - (bar U_1 + bar V_1) = 4 - (4 +4) = color{blue}{-4} `
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `bar U_i` | `S_1` | 4 [-4] | 8(25) | 8(41) | 0 | | 10 | `4` | `S_2` | 16(62) | 24 | 16 | 0(20) | | 0 | -- | `S_3` | 8 | 16(77) | 24 | 0 | | 0 | -- | | Demand | 10 | 0 | 0 | 0 | | | | `bar V_j` | `4` | -- | -- | -- | | | |
The most negative `Delta_(ij)` is -4 in cell `S_1 D_1`
The allocation to this cell is min(10,10) = 10. Table-6: This leads to the following table
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4 (10) | 8 (25) | 8 (41) | 0 | | 0 | `S_2` | 16 (62) | 24 | 16 | 0 (20) | | 0 | `S_3` | 8 | 16 (77) | 24 | 0 | | 0 | | Demand | 0 | 0 | 0 | 0 | | |
Initial feasible solution is
| `D_1` | `D_2` | `D_3` | `D_(dummy)` | | Supply | `S_1` | 4 (10) | 8 (25) | 8 (41) | 0 | | 76 | `S_2` | 16 (62) | 24 | 16 | 0 (20) | | 82 | `S_3` | 8 | 16 (77) | 24 | 0 | | 77 | | Demand | 72 | 102 | 41 | 20 | | |
The minimum total transportation cost `= 4 xx 10 + 8 xx 25 + 8 xx 41 + 16 xx 62 + 0 xx 20 + 16 xx 77 = 2792`
Here, the number of allocated cells = 6 is equal to m + n - 1 = 3 + 4 - 1 = 6 `:.` This solution is non-degenerate
This material is intended as a summary. Use your textbook for detail explanation. Any bug, improvement, feedback then
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