利用最小元素法求出运筹学运输问题的初始解然后用闭合回路法判断并且调整为最优解的算法
时间: 2024-02-26 16:56:37 浏览: 21
好的,下面是利用最小元素法求出运筹学运输问题的初始解并用闭合回路法判断并调整为最优解的 Python 代码:
```python
import numpy as np
# 输入相关数据
supply = np.array([10, 20, 30]) # 供应商每个仓库的供应量
demand = np.array([20, 30, 10, 10]) # 需求方每个销售点的需求量
cost = np.array([[2, 3, 1, 4], [5, 4, 8, 1], [3, 6, 2, 5]]) # 运输成本矩阵
# 最小元素法求初始解
allocation = np.zeros((3, 4))
while np.sum(supply) > 0 and np.sum(demand) > 0:
# 找到成本最小的元素
min_cost = np.min(cost)
min_cost_index = np.argwhere(cost == min_cost)
row = min_cost_index[0][0]
col = min_cost_index[0][1]
# 分配货物
amount = min(supply[row], demand[col])
allocation[row, col] = amount
supply[row] -= amount
demand[col] -= amount
# 将已分配的成本设为极大值
cost[row, col] = np.inf
# 闭合回路法求最优解
while True:
# 计算各个销售点的运输量
sales_amount = np.sum(allocation, axis=0)
# 计算各个供应商的运输量
supply_amount = np.sum(allocation, axis=1)
# 找到存在缺货的销售点
shortage_index = np.argwhere(sales_amount < demand)
if len(shortage_index) == 0:
break
# 找到缺货销售点的缺货量
shortage = demand[shortage_index[0][0]] - sales_amount[shortage_index[0][1]]
# 找到从该销售点出发、经过未分配路径、返回该销售点的路径
for i in range(allocation.shape[0]):
for j in range(allocation.shape[1]):
if allocation[i, j] > 0:
# 判断路径是否符合条件
if i in shortage_index and j not in shortage_index:
path = [(i, j)]
current_row = i
current_col = j
while current_col != shortage_index[0][1]:
next_row, next_col = np.argwhere(allocation[current_row,:] > 0)[0]
path.append((next_row, next_col))
current_row = next_row
current_col = next_col
# 找到回路中最小的分配量
min_amount = np.min([allocation[row, col] for row, col in path])
# 调整路径上的分配量
for row, col in path:
allocation[row, col] -= min_amount
elif i not in shortage_index and j in shortage_index:
path = [(i, j)]
current_row = i
current_col = j
while current_row != shortage_index[0][0]:
next_row, next_col = np.argwhere(allocation[:,current_col] > 0)[0]
path.append((next_row, next_col))
current_row = next_row
current_col = next_col
# 找到回路中最小的分配量
min_amount = np.min([allocation[row, col] for row, col in path])
# 调整路径上的分配量
for row, col in path:
allocation[row, col] -= min_amount
# 输出最优解
total_cost = np.sum(allocation * cost)
print("最优解为:")
print(allocation)
print("总成本为:", total_cost)
```
这段代码实现了利用最小元素法求出运筹学运输问题的初始解,并用闭合回路法判断并调整为最优解。你可以根据自己的需求进行修改。