python - 在 pyswarm 中选择初始位置(粒子群优化)

Question

我正在优化问题中应用 PSO。我有一个成本函数 c(x)，其中 x 是一个 n 维数组。使用 pyswarms 可以使用以下方法计算最小值

swarm_size = 200
dim = len(X)      # Dimension of X
epsilon = 1.0
options = {'c1': 1.7, 'c2':1.7, 'w':0.729}
bdmin = np.array(bdmin)
bdmax = np.array(bdmax)


constraints = (bdmin,bdmax)
optimizer = ps.single.GlobalBestPSO(n_particles=swarm_size,
                                dimensions=dim,
                                options=options,
                                bounds=constraints)

cost, joint_vars = optimizer.optimize(opt_func, iters=1000)

然而，由于收敛速度很慢，而且我知道应该是什么向量 x 其结果是 c(x) 的最小值，我想通知算法从哪里开始群体。我尝试使用 pyswarms 文档中描述的参数 init_pos。

init_pos = np.array(init_pos) #My guess for a initial swarm

在这种情况下，变量 init_pos 是一个大小为 (len(X),) 的数组。但是，当我执行代码时

optimizer = ps.single.GlobalBestPSO(n_particles=swarm_size,
                                dimensions=dim,
                                options=options,
                                bounds=constraints,
                                init_pos = init_pos)

我收到以下错误:

Traceback (most recent call last):

File "<ipython-input-110-f2477b03016c>", line 1, in <module>
runfile('/home/lps/Downloads/pso.py', wdir='/home/lps/Downloads')

File "/home/lps/anaconda3/lib/python3.7/site- 
packages/spyder_kernels/customize/spydercustomize.py", line 668, in 
runfile
execfile(filename, namespace)

File "/home/lps/anaconda3/lib/python3.7/site- 
packages/spyder_kernels/customize/spydercustomize.py", line 108, in 
execfile
exec(compile(f.read(), filename, 'exec'), namespace)

File "/home/lps/Downloads/pso.py", line 234, in <module>
init_pos = init_pos)

File "/home/lps/anaconda3/lib/python3.7/site- 
packages/pyswarms/single/global_best.py", line 132, in __init__
init_pos=init_pos,

File "/home/lps/anaconda3/lib/python3.7/site- 
packages/pyswarms/base/base_single.py", line 110, in __init__
self.reset()

File "/home/lps/anaconda3/lib/python3.7/site- 
packages/pyswarms/base/base_single.py", line 197, in reset
options=self.options,

File "/home/lps/anaconda3/lib/python3.7/site- 
packages/pyswarms/backend/generators.py", line 245, in create_swarm
return Swarm(position, velocity, options=options)

File "<attrs generated init 
73b4f2f5e7b2bdb45fae355f5990e313431ea4d3>", line 11, in __init__
self.dimensions = __attr_factory_dimensions(self)

File "/home/lps/anaconda3/lib/python3.7/site- 
packages/pyswarms/backend/swarms.py", line 117, in dimensions_default
return self.position.shape[1]

IndexError: tuple index out of range

init_pos的正确使用方法是什么？范围？

Answer 1

Pyswarms 的作者在这里:)
init_pos尺寸应该是 (swarm_size, num_dimensions) .然而，正如你所说:

n this case, the variable init_pos is an array of size (len(X),). However, when I execute the code

由于您传递的是一维数组，因此会出错。同样，要解决此问题，请初始化您的位置矩阵，使其具有二维。

希望能帮助到你!