, out_name='', variable_style=None, function_style=None)[source]

Returns a trainer extension to dump a computational graph.

This extension dumps a computational graph. The graph is output in DOT language.

It only dumps a graph at the first invocation.


As of v2.0.0, the computational graph is not kept by default. This extension changes this behavior until the first invocation. It is strongly recommended to use it with the default trigger setting.

The detailed behavior of this extension since v2.0.0 is as follows.

  1. In its initializer, it turns on the chainer.config.keep_graph_on_report flag.
  2. At the first iteration, it dumps the graph using the graph held by the reported variable.
  3. After dumping the graph, it turns off the flag (if it was originally turned off) so that any variable reported afterward does not hold a computational graph.

When the keep_graph_on_report flag is turned on, the computational graph created by the updater is kept during the invocation of extensions. It will cause an unnecessarily large memory consumption when an extension also uses a large amount of memory, e.g. Evaluator.

With the default setting, the dump_graph extension is called at the first iteration. Since Evaluator is not called at the first iteration in most cases, it does not cause any memory problem.

  • root_name (str) – Name of the root of the computational graph. The root variable is retrieved by this name from the observation dictionary of the trainer.
  • out_name (str) – Output file name.
  • variable_style (dict) – Dot node style for variables. Each variable is rendered by an octagon by default.
  • function_style (dict) – Dot node style for functions. Each function is rendered by a rectangular by default.

See also

See build_computational_graph() for the variable_style and function_style arguments.