Class Topic<Value>

constructor

• new Topic<Value>(
      fields?: { accumulate?: boolean; unique?: boolean },
  ): Topic<Value>

  Type Parameters

  • Value

  Parameters

  • Optionalfields: { accumulate?: boolean; unique?: boolean }

    • Optionalaccumulate?: boolean

      Whether to accumulate values across steps. If false, the channel will be emptied after each step.

    • Optionalunique?: boolean

      Whether to only add unique values to the topic. If true, only unique values (using reference equality) will be added to the topic.

  Returns Topic<Value>

accumulate

lc_graph_name

seen

unique

values

checkpoint

• checkpoint(): [Value[], Value[]]

  Return a string representation of the channel's current state.

  Returns [Value[], Value[]]

  Throws

  if the channel is empty (never updated yet), or doesn't support checkpoints.

fromCheckpoint

• fromCheckpoint(checkpoint?: [Value[], Value[]]): this

  Return a new identical channel, optionally initialized from a checkpoint. Can be thought of as a "restoration" from a checkpoint which is a "snapshot" of the channel's state.

  Parameters

  • Optionalcheckpoint: [Value[], Value[]]

  Returns this

get

• get(): Value[]

  Return the current value of the channel.

  Returns Value[]

  Throws

  if the channel is empty (never updated yet).

isAvailable

• isAvailable(): boolean

  Return True if the channel is available (not empty), False otherwise. Subclasses should override this method to provide a more efficient implementation than calling get() and catching EmptyChannelError.

  Returns boolean

update

• update(values: (Value | Value[])[]): boolean

  Update the channel's value with the given sequence of updates. The order of the updates in the sequence is arbitrary. This method is called by Pregel for all channels at the end of each step. If there are no updates, it is called with an empty sequence.

  Raises InvalidUpdateError if the sequence of updates is invalid. Returns True if the channel was updated, False otherwise.

  Parameters

  • values: (Value | Value[])[]

  Returns boolean

  Throws

  if the sequence of updates is invalid.