use Channel;


import Channel;

Support for channels that can transfer typed data between tasks.

This module contains the implementation of channels which can be used to move typed data between Chapel tasks.

A channel is a parallel-safe data structure that provides a mechanism for concurrently executing functions to communicate by sending and receiving values of a specified element type. A channel can be buffered or unbuffered. A buffered channel has a maximum capacity specified by bufferSize. There are mainly three operations that can be performed on a channel.

The channel operations are blocking, i.e., the calling task will be suspended if an operation cannot be completed. The channel follows First-In-First-Out mechanism, i.e., the first value sent to the channel will be received first.

record channel
type eltType
var channelObj: shared chan(eltType)
proc init(type eltType, size = 0)

Initialize a channel

  • elt : type – The element type used for sending and receiving

  • size : int – Specify the maximum capacity for the channel bufferSize.

proc lock()
proc unlock()
proc recv(out val: eltType): bool

Receive the first value in the channel buffer. It will suspend the calling task, until data is sent to the channel. If the channel is closed and the buffer is empty, it will return false indicating that the receive operation was not successful.


val : eltType – Storage for the received value.


true if the receive was successful, else false.

Return type


proc send(in val: eltType) throws

Send a value to the channel buffer. If the buffer is at maximum capacity it will suspend the waiting task, until there is space in the buffer or a receiving task awakes it. If a channel is closed no more data can be sent to it.


val : eltType – Data to be sent to the channel


ChannelError – If send is called on a closed channel.

proc close() throws

This function is used to close a channel indicating that no more data can be sent to it.


ChannelError – If called on a closed channel.

iter these()

Iterator to receive data from the channel until it is closed.