Hierarchical Even Number Generator

Assuming you have seen the basics from the Sine Generator, this section will describe a simplistic even number generator, using hierarchical CBD modelling.

At every timestep in the model, the generator is required to output its double. We can split it up into two components: a CBD.lib.std.TimeBlock and a Double CBD class, which computes the double of its input. The generator block can be constructed just like the SinGen block was created in the Sine Generator example:

from CBD.Core import CBD
from CBD.lib.std import TimeBlock

class EvenNumberGen(CBD):
    def __init__(self, name="EvenNumberGen"):
        CBD.__init__(self, name, input_ports=[], output_ports=["OUT1"])

        self.addBlock(TimeBlock("time"))
        self.addBlock(Double("double"))

        self.addConnection("time", "double", output_port_name='OUT1',
                                             input_port_name='IN1')
        self.addConnection("double", "OUT1", output_port_name='OUT1')


numGen = EvenNumberGen("NumGen")

Now, we’re left with the construction of the Double block, which basically multiplies its input with 2:

from CBD.lib.std import ProductBlock, ConstantBlock

class Double(CBD):
    def __init__(self, name="Double"):
        CBD.__init__(self, name, input_ports=["IN1"], output_ports=["OUT1"])

        # Create the blocks
        self.addBlock(ConstantBlock("two", 2))
        self.addBlock(ProductBlock("mult"))

        # Connect the blocks
        # Default ports are "INx" and "OUT1", with 'x' the index of the connection
        self.addConnection("two", "mult")
        self.addConnection("IN1", "mult")
        self.addConnection("mult", "OUT1")

And that’s it. Now your models can have hierarchy!

Flattening

Of course, when building highly hierarchical models, it may be useful to be able to create a full model, ignoring all hierarchical model conceptions. Flattening is the reverse of hierarchical composition. By calling the CBD.Core.CBD.flatten() method, the CBD model will be transformed into a single CBD model without hierarchy.