⭕ Intro¶
In this section we will cover the basic CLI usage of NNViz, which is probably the most common use case for quickly glancing at a model inner structure. I will try to keep it as simple as possible, gradually adding more advanced features as we go.
Visualizing a Model¶
Visualizing a model with NNViz is very simple. This is the minimal command that you need to run, keeping all the options at their default values. We will use a resnet18 model from torchvision as an example.
nnviz resnet18
This command will generate a file called resnet18.pdf in your current working directory. This file contains a visualization of the model, which you can open with any PDF viewer, like your internet browser.
Note
By default, NNViz automatically loads models from the torchvision.models module. This is done because it is very common to use models from this module, and it is a bit annoying to have to write torchvision.models.XXX every time. If you want to use a model from somewhere else, just pass the full path to a function that returns the model, like my_module.my_model.
The generated PDF file will look something like this:
Resnet18 visualized with NNViz CLI
By default, you will get a (hopefully) clear graph representation of all the model operations, up to a certain level of nesting. We will later see how to change this behavior, but for now, let’s just focus on the default visualization. The top portion of the graph contains a title and where does the model come from, in my case torchvision.models.resnet, along with the torchvision version (0.13.1). The graph starts and ends with two nodes named Input and Output, each reporting also the identifier name. All the nodes in between represent the exact operations that are performed by the model in its forward pass. Each of them has a title that describes the operation, an identifier, the absolute and relative number of parameters and the source code location.
Some nodes are wrapped in gray boxes, which means that they are nested inside other nodes. We will see later how to change this behavior, increasing or decreasing the maximum level of nesting.
Getting Help¶
You can print a CLI help message by running:
nnviz --help
This will print a full list of all the available options, default values, and descriptions. You can also refer to this documentation for more in-depth explanations of the CLI functionality.
Auto-Opening the Output¶
By default, NNViz will not open the generated PDF file automatically, but you can change this behavior by passing the -s or --show flag:
nnviz resnet18 -s
And you will notice that the default PDF viewer will open automatically, displaying the generated visualization.