docs/source/en/modular_diffusers/modular_diffusers_states.md
Blocks rely on the [~modular_pipelines.PipelineState] and [~modular_pipelines.BlockState] data structures for communicating and sharing data.
| State | Description |
|---|---|
[~modular_pipelines.PipelineState] | Maintains the overall data required for a pipeline's execution and allows blocks to read and update its data. |
[~modular_pipelines.BlockState] | Allows each block to perform its computation with the necessary data from inputs |
This guide explains how states work and how they connect blocks.
The [~modular_pipelines.PipelineState] is a global state container for all blocks. It maintains the complete runtime state of the pipeline and provides a structured way for blocks to read from and write to shared data.
[~modular_pipelines.PipelineState] stores all data in a values dict, which is a mutable state containing user provided input values and intermediate output values generated by blocks. If a block modifies an input, it will be reflected in the values dict after calling set_block_state.
PipelineState(
values={
'prompt': 'a cat'
'guidance_scale': 7.0
'num_inference_steps': 25
'prompt_embeds': Tensor(dtype=torch.float32, shape=torch.Size([1, 1, 1, 1]))
'negative_prompt_embeds': None
},
)
The [~modular_pipelines.BlockState] is a local view of the relevant variables an individual block needs from [~modular_pipelines.PipelineState] for performing it's computations.
Access these variables directly as attributes like block_state.image.
BlockState(
image: <PIL.Image.Image image mode=RGB size=512x512 at 0x7F3ECC494640>
)
When a block's __call__ method is executed, it retrieves the [BlockState] with self.get_block_state(state), performs it's operations, and updates [~modular_pipelines.PipelineState] with self.set_block_state(state, block_state).
def __call__(self, components, state):
# retrieve BlockState
block_state = self.get_block_state(state)
# computation logic on inputs
# update PipelineState
self.set_block_state(state, block_state)
return components, state
[~modular_pipelines.PipelineState] and [~modular_pipelines.BlockState] interaction is defined by a block's inputs, and intermediate_outputs.
inputs, a block can modify an input - like block_state.image - and this change can be propagated globally to [~modular_pipelines.PipelineState] by calling set_block_state.intermediate_outputs, is a new variable that a block creates. It is added to the [~modular_pipelines.PipelineState]'s values dict and is available as for subsequent blocks or accessed by users as a final output from the pipeline.