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"try:\n",
" from openmdao.utils.notebook_utils import notebook_mode # noqa: F401\n",
"except ImportError:\n",
" !python -m pip install openmdao[notebooks]"
]
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"# Basics of Creating N2 Model Visualizations\n",
"\n",
"An OpenMDAO model can have a number of connections, and several different residuals being converged.\n",
"Trying to keep track of all the connections in your head can be a bit challenging, but OpenMDAO offers\n",
"some visualization tools to help see what's going on. This page explains the basics of generating an N2 diagram\n",
"either from the command line or from a script.\n",
"\n",
"An N2 diagram, also known as an N-squared diagram, is a diagram in the shape of a matrix, representing functional or\n",
"physical interfaces between system elements. It is used to systematically identify, define, tabulate, design, and\n",
"analyze functional and physical interfaces. It applies to system interfaces and hardware and/or software interfaces.\n",
"For more information, see [N2_chart](https://en.wikipedia.org/wiki/N2_chart).\n",
"\n",
"For this page, we will be using this code example. Notice that there is an error in this code because one of the\n",
"connection lines has been commented out. This was done to show how the N2 diagram can help point out unconnected\n",
"inputs quickly."
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"data": {
"application/papermill.record/text/html": "class Resistor(om.ExplicitComponent):\n """Computes current across a resistor using Ohm's law."""\n\n def initialize(self):\n self.options.declare('R', default=1., desc='Resistance in Ohms')\n\n def setup(self):\n self.add_input('V_in', units='V')\n self.add_input('V_out', units='V')\n self.add_output('I', units='A')\n\n def setup_partials(self):\n self.declare_partials('I', 'V_in', method='cs')\n self.declare_partials('I', 'V_out', method='cs')\n\n def compute(self, inputs, outputs):\n deltaV = inputs['V_in'] - inputs['V_out']\n outputs['I'] = deltaV / self.options['R']\nclass Diode(om.ExplicitComponent):\n """Computes current across a diode using the Shockley diode equation."""\n\n def initialize(self):\n self.options.declare('Is', default=1e-15, desc='Saturation current in Amps')\n self.options.declare('Vt', default=.025875, desc='Thermal voltage in Volts')\n\n def setup(self):\n self.add_input('V_in', units='V')\n self.add_input('V_out', units='V')\n self.add_output('I', units='A')\n\n def setup_partials(self):\n self.declare_partials('I', 'V_in', method='cs')\n self.declare_partials('I', 'V_out', method='cs')\n\n def compute(self, inputs, outputs):\n deltaV = inputs['V_in'] - inputs['V_out']\n Is = self.options['Is']\n Vt = self.options['Vt']\n outputs['I'] = Is * (np.exp(deltaV / Vt) - 1)\nclass Node(om.ImplicitComponent):\n """Computes voltage residual across a node based on incoming and outgoing current."""\n\n def initialize(self):\n self.options.declare('n_in', default=1, types=int, desc='number of connections with + assumed in')\n self.options.declare('n_out', default=1, types=int, desc='number of current connections + assumed out')\n\n def setup(self):\n self.add_output('V', val=5., units='V')\n\n for i in range(self.options['n_in']):\n i_name = 'I_in:{}'.format(i)\n self.add_input(i_name, units='A')\n\n for i in range(self.options['n_out']):\n i_name = 'I_out:{}'.format(i)\n self.add_input(i_name, units='A')\n\n def setup_partials(self):\n #note: we don't declare any partials wrt `V` here,\n # because the residual doesn't directly depend on it\n self.declare_partials('V', 'I*', method='cs')\n\n def apply_nonlinear(self, inputs, outputs, residuals):\n residuals['V'] = 0.\n for i_conn in range(self.options['n_in']):\n residuals['V'] += inputs['I_in:{}'.format(i_conn)]\n for i_conn in range(self.options['n_out']):\n residuals['V'] -= inputs['I_out:{}'.format(i_conn)]\n