实例化Dymos中Birkhoff转录时出现KeyError错误

运行以下代码时触发KeyError：

import dymos as dm
tx = dm.Birkhoff(num_nodes=5)

报错信息：

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
File ~/miniconda3/envs/cp2/lib/python3.11/site-packages/openmdao/utils/options_dictionary.py:514, in OptionsDictionary.__setitem__(self, name, value)
    513 try:
---> 514     meta = self._dict[name]
    515 except KeyError:
    516     # The key must not have been declared.

KeyError: 'num_nodes'

During handling of the above exception, another exception occurred:

KeyError                                  Traceback (most recent call last)
Cell In[2], line 1
----> 1 dm.Birkhoff(num_nodes=5)

File ~/miniconda3/envs/cp2/lib/python3.11/site-packages/dymos/transcriptions/pseudospectral/birkhoff.py:30, in Birkhoff.__init__(self, **kwargs)
     29 def __init__(self, **kwargs):
---> 30     super(Birkhoff, self).__init__(**kwargs)
     31     self._rhs_source = 'ode_iter_group.ode_all'

File ~/miniconda3/envs/cp2/lib/python3.11/site-packages/dymos/transcriptions/transcription_base.py:46, in TranscriptionBase.__init__(self, **kwargs)
     44 self._declare_options()
     45 self.initialize()
---> 46 self.options.update(kwargs)
     47 self.init_grid()
     49 # Where to query var info.

File ~/miniconda3/envs/cp2/lib/python3.11/site-packages/openmdao/utils/options_dictionary.py:473, in OptionsDictionary.update(self, in_dict)
    464 """
    465 Update the internal dictionary with the given one.
    466
   (...)
    470     The incoming dictionary to add to the internal one.
    471 """
    472 for name in in_dict:
---> 473     self[name] = in_dict[name]

File ~/miniconda3/envs/cp2/lib/python3.11/site-packages/openmdao/utils/options_dictionary.py:517, in OptionsDictionary.__setitem__(self, name, value)
    514     meta = self._dict[name]
    515 except KeyError:
    516     # The key must not have been declared.
---> 517     self._raise(f"Option '{name}' cannot be set because it has not been declared.",
    518                 exc_type=KeyError)
    520 if self._read_only:
    521     self._raise(f"Tried to set read-only option '{name}'.", exc_type=KeyError)

File ~/miniconda3/envs/cp2/lib/python3.11/site-packages/openmdao/utils/options_dictionary.py:245, in OptionsDictionary._raise(self, msg, exc_type)
    243 else:
    244     full_msg = '{}: {}'.format(self._parent_name, msg)
---> 245 raise exc_type(full_msg)

KeyError: "Option 'num_nodes' cannot be set because it has not been declared."

当前环境：dymos 1.10.0，openmdao 3.34.2，怀疑是版本适配问题，想确认Birkhoff转录对应的OpenMDAO版本，或排查其他原因。

1. 直接原因：参数传递错误 #

num_nodes不是dm.Birkhoff类的初始化参数，该参数属于dm.Phase的配置项，用来控制转录的节点数量。正确用法是在创建Phase时指定节点数，而非直接传给Birkhoff构造函数：

import dymos as dm
from openmdao.api import Problem

prob = Problem()
# 示例：创建Phase时指定转录和节点数
phase = prob.model.add_subsystem('phase0', dm.Phase(
    transcription=dm.Birkhoff(),
    num_nodes=5,
    ode_class=YourODEClass  # 替换为实际的ODE类
))

2. 版本兼容性说明 #

Dymos 1.10.0官方兼容的OpenMDAO版本范围是3.25.0 ~ 3.34.x，你当前使用的OpenMDAO 3.34.2在兼容范围内，版本不是导致该错误的原因。

3. 额外排查点 #

• 确认Dymos安装完整：若安装过程中出现损坏，可能导致类参数声明异常，可尝试重新安装Dymos 1.10.0：

  pip install --force-reinstall dymos==1.10.0
  

• 检查代码是否混淆了转录类与Phase的参数：所有节点数、时间范围等配置都应在Phase层级设置，转录类仅负责数值方法的实现。

内容的提问来源于stack exchange，提问作者wonderboy3489