在向量上使用标准会导致CVXPY中的错误

我正在为一些代码苦苦挣扎。我正在尝试为2D轨迹运行凸优化，并且我试图最小化速度差异。问题是当前速度的计算（通过使用我的溶液向量x中的时间步长t-1和t + 1中），但是当我尝试创建一个新的向量使用凸模法在向量上使用标准会导致CVXPY中的错误

import cvxpy as cvx 

#costFunction, sum integral 
def costFunction(x): 
    outputSum = 0.0 
    for i in range(1,amountSamplePoints): 
     outputSum = outputSum + (getJvel(i,x)) * 0.5 
    return outputSum 

#get velocity at time t 
def getVel(t,x): 
    x2=x[2*(t+1)] 
    y2=x[2*(t+1)+1] 
    x1=x[2*(t-1)] 
    y1=x[2*(t-1)+1] 
    #return cvx.norm(x[2*(t-1):2*t:1]) 
    return cvx.norm([x2-x1,y2-y1]) 

def getJvel(t,x): 
    return cvx.square(20.0-getVel(t,x)) 

# Problem data. 
x = cvx.Variable(12) 

# Construct the problem. 
objective = cvx.Minimize(costFunction(x)) 
constraints = [] 
prob = cvx.Problem(objective, constraints) 
prob.solve()

的问题发生

我得到：

>>> (executing file "sampleCode.py") 
Traceback (most recent call last): 
    File "/home/fornubuntu/Documents/Python Projects/sampleCode.py", line 26, in <module> 
    objective = cvx.Minimize(costFunction(x)) 
    File "/home/fornubuntu/Documents/Python Projects/sampleCode.py", line 7, in costFunction 
    outputSum = outputSum + (getJvel(i,x)) * 0.5 
    File "/home/fornubuntu/Documents/Python Projects/sampleCode.py", line 20, in getJvel 
    return cvx.square(20.0-getVel(t,x)) 
    File "/home/fornubuntu/Documents/Python Projects/sampleCode.py", line 17, in getVel 
    return cvx.norm([x2-x1,y2-y1]) 
    File "/home/fornubuntu/anaconda3/lib/python3.5/site-packages/cvxpy/atoms/norm.py", line 41, in norm 
    x = Expression.cast_to_const(x) 
    File "/home/fornubuntu/anaconda3/lib/python3.5/site-packages/cvxpy/expressions/expression.py", line 238, in cast_to_const 
    return expr if isinstance(expr, Expression) else cvxtypes.constant()(expr) 
    File "/home/fornubuntu/anaconda3/lib/python3.5/site-packages/cvxpy/expressions/constants/constant.py", line 42, in __init__ 
    self._value = intf.DEFAULT_INTF.const_to_matrix(value) 
    File "/home/fornubuntu/anaconda3/lib/python3.5/site-packages/cvxpy/interface/base_matrix_interface.py", line 47, in new_converter 
    if not convert_scalars and cvxpy.interface.matrix_utilities.is_scalar(value): 
    File "/home/fornubuntu/anaconda3/lib/python3.5/site-packages/cvxpy/interface/matrix_utilities.py", line 150, in is_scalar 
    return size(constant) == (1, 1) 
    File "/home/fornubuntu/anaconda3/lib/python3.5/site-packages/cvxpy/interface/matrix_utilities.py", line 131, in size 
    return (len(constant[0]), len(constant)) 
TypeError: object of type 'AddExpression' has no len()

任何想法/提示？感谢很多提前

来源

2016-11-29 fornubitu

如果问题是在该行：

return cvx.norm([x2-x1,y2-y1])

可以使用vstack如下：

return cvx.norm(cvx.vstack(x2-x1,y2-y1))

vstack创建一个数组，CVX可以处理。

来源

2018-01-24 15:27:46 choff

在向量上使用标准会导致CVXPY中的错误

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