Token-based flow control of messages in a parallel computer

A method of token-based flow control of messages in a parallel computer executing a plurality of parallel operations, the parallel computer including a plurality of compute nodes operatively coupled for data communications over one or more data communications networks, each compute node including one or more computer processors, the method comprising:

• allocating, by a token administration module to a plurality of the computer processors in the parallel computer, a number of data communications tokens, wherein:
• each data communications token represents an amount of data that a computer processor may send to a destination;
• and
• the number of data communications tokens allocated to each computer processor is determined in dependence upon token distribution rules;
• identifying, by the token administration module for each computer processor, all communicators executing on the computer processor, wherein each communicator is participating in a distinct parallel operation executing on the parallel computer;
• allocating, by the token administration module to the communicators, the data communications tokens;
• determining, by a communicator attempting to send data to the destination, whether the communicator has enough available data communications tokens to send the data to the destination;
• and
• responsive to determining that the communicator has enough available data communications tokens to send the data, sending, by the communicator, the data to the destination.