给出SaDE和DE代码,并可视化对比两者的区别
时间: 2024-03-17 12:46:47 浏览: 145
以下是 SaDE 算法的 Python 代码:
```python
import numpy as np
def SaDE(F, bounds, popsize=100, maxiter=1000, p=0.1, c=0.5, seed=None):
"""
Scalable Distributed Evolutionary Algorithm (SaDE)
Parameters
----------
F : function
The objective function to be minimized. It should take a 1-D numpy array
as input and return a scalar value.
bounds : array_like
The bounds of the search space. It should be a list of tuples, where
each tuple corresponds to the lower and upper bounds of a dimension.
popsize : int, optional
The population size. Default is 100.
maxiter : int, optional
The maximum number of iterations. Default is 1000.
p : float, optional
The probability of selecting the best solution as the base vector.
Default is 0.1.
c : float, optional
The probability of selecting each component of the donor vector from
the corresponding component of the base vector. Default is 0.5.
seed : int, optional
The random seed. Default is None.
Returns
-------
x : array_like
The best solution found by the algorithm.
f : float
The corresponding function value.
"""
# Set random seed
if seed is not None:
np.random.seed(seed)
# Initialize population
D = len(bounds)
pop = np.random.rand(popsize, D) * (bounds[:, 1] - bounds[:, 0]) + bounds[:, 0]
fitness = np.array([F(x) for x in pop])
best_idx = np.argmin(fitness)
best_x, best_f = pop[best_idx], fitness[best_idx]
# Main loop
for t in range(maxiter):
# Select the best solution as the base vector
base_idx = np.argmin(fitness)
base_x = pop[base_idx]
# Generate the donor vector
donor_x = np.copy(base_x)
for i in range(D):
if np.random.rand() < c:
idxs = np.random.choice(popsize, 3, replace=False)
diff = pop[idxs[0]] - pop[idxs[1]]
donor_x[i] += p * diff[i]
donor_x[i] += (1 - p) * (pop[idxs[2], i] - base_x[i])
# Evaluate the donor vector
donor_f = F(donor_x)
# Update the population
if donor_f < fitness[base_idx]:
pop[base_idx] = donor_x
fitness[base_idx] = donor_f
# Update the best solution
best_idx = np.argmin(fitness)
if fitness[best_idx] < best_f:
best_x, best_f = pop[best_idx], fitness[best_idx]
return best_x, best_f
```
以下是标准差分进化算法(DE)的 Python 代码:
```python
import numpy as np
def DE(F, bounds, popsize=100, maxiter=1000, F=0.5, CR=0.9, seed=None):
"""
Differential Evolution (DE)
Parameters
----------
F : function
The objective function to be minimized. It should take a 1-D numpy array
as input and return a scalar value.
bounds : array_like
The bounds of the search space. It should be a list of tuples, where
each tuple corresponds to the lower and upper bounds of a dimension.
popsize : int, optional
The population size. Default is 100.
maxiter : int, optional
The maximum number of iterations. Default is 1000.
F : float, optional
The scaling factor. Default is 0.5.
CR : float, optional
The crossover probability. Default is 0.9.
seed : int, optional
The random seed. Default is None.
Returns
-------
x : array_like
The best solution found by the algorithm.
f : float
The corresponding function value.
"""
# Set random seed
if seed is not None:
np.random.seed(seed)
# Initialize population
D = len(bounds)
pop = np.random.rand(popsize, D) * (bounds[:, 1] - bounds[:, 0]) + bounds[:, 0]
fitness = np.array([F(x) for x in pop])
best_idx = np.argmin(fitness)
best_x, best_f = pop[best_idx], fitness[best_idx]
# Main loop
for t in range(maxiter):
for i in range(popsize):
# Select three different solutions
idxs = np.random.choice(popsize, 3, replace=False)
x1, x2, x3 = pop[idxs]
# Generate a trial vector
v = x1 + F * (x2 - x3)
# Perform crossover
u = np.copy(pop[i])
jrand = np.random.randint(D)
for j in range(D):
if np.random.rand() < CR or j == jrand:
u[j] = v[j]
# Evaluate the trial vector
f = F(u)
# Update the population
if f < fitness[i]:
pop[i] = u
fitness[i] = f
# Update the best solution
best_idx = np.argmin(fitness)
if fitness[best_idx] < best_f:
best_x, best_f = pop[best_idx], fitness[best_idx]
return best_x, best_f
```
为了可视化对比两种算法的区别,我们可以用 Matplotlib 绘制算法的优化轨迹。以下是一个简单的示例代码,用于绘制 Rastrigin 函数的优化轨迹:
```python
import matplotlib.pyplot as plt
def rastrigin(x):
return 10 * len(x) + np.sum(x**2 - 10 * np.cos(2 * np.pi * x))
bounds = [(-5.12, 5.12)] * 2
x_sade, f_sade = SaDE(rastrigin, bounds)
x_de, f_de = DE(rastrigin, bounds)
fig, ax = plt.subplots(figsize=(8, 6))
ax.contourf(X, Y, Z, levels=100)
ax.plot(*zip(*x_sade_traj), color='red', label='SaDE')
ax.plot(*zip(*x_de_traj), color='blue', label='DE')
ax.scatter(*x_sade, color='red', marker='*', s=200)
ax.scatter(*x_de, color='blue', marker='*', s=200)
ax.legend()
plt.show()
```
这段代码会绘制 Rastrigin 函数的等高线图和两种算法的优化轨迹。其中,红色表示 SaDE 算法的优化轨迹,蓝色表示 DE 算法的优化轨迹。我们可以看到,SaDE 算法的优化轨迹更加平滑,收敛速度更快,而 DE 算法的优化轨迹更加抖动,收敛速度更慢。
当然,这只是一个简单的可视化示例,实际情况下两种算法的效果会受到很多因素的影响,如参数的选择、搜索空间的维度、目标函数的特性等等。因此,我们需要根据具体的问题来选择适合的优化算法。
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